reasampler/COMPLETED.md

# COMPLETED.md — ReaSampler landed milestones

Completed milestone entries removed from `PLAN.md`. Each entry preserves its
original Goal, Verify, and checklist points with boxes marked done.

---

## Milestone 0 — Transition scaffold: reaper_mpeview → ReaSampler
**Goal:** Retire the MPE scaffold and stand up the sampler's pure core in its
place, preserving the pure-core / REAPER-shell split.
**Verify:** `cmake -B build -S .` configures clean; `cmake --build build` builds
the renamed extension target and the pure-core test target; `ctest --test-dir
build` is green with the new `bank_model` + `peaks` suites present.

- [x] Delete `src/mpe_model.{h,cpp}` and `src/mpe_view.{h,cpp}`; remove
  `tests/test_mpe_model.cpp`.
- [x] Rename the CMake `project()` and the extension MODULE target from
  `reaper_mpeview` to `reaper_reasampler` (binary `OUTPUT_NAME` likewise);
  update `PREFIX ""` / platform SUFFIX blocks to the new target name.
- [x] Replace the pure `mpe_model` static lib + `mpe_model_tests` executable with
  `bank_model` (pure static lib) + `bank_model_tests`; keep the CTest wiring.
- [x] Repoint `src/main.cpp`: drop the `mpe_view.h` include and all `MpeView_*`
  calls (toggle / IsOpen / OnTimer / Cleanup); stub the extension entry so it
  loads, logs to console, and registers nothing MPE-specific. The
  `command_id` / `gaccel` / `hookcommand` registration *pattern* is preserved for
  reuse (CLAUDE.md §REAPER extension contract) — the MPE action string is removed.
- [x] Choose and record the persistent action-id prefix for the sampler family
  (replaces `CEREBELLUM_MPEVIEW_TOGGLE`); this string is forever-stable once
  shipped (CLAUDE.md §action registration).
- [x] Refresh `README.md` layout/next-step sections to the sampler module set.
  (Landed-work reflection is doc-keeper's; this point exists so the stale MPE
  README does not mislead the first implementer.)

---

## Milestone 1 — bank_model + JSON round-trip (pure)
**Goal:** The `Sample` metadata struct and `BankIndex` (add / remove / query /
tier moves / dedup-by-hash) with JSON serialize/deserialize to `std::string`.
CONTEXT.md §Data model, §Module architecture.
**Verify:** CTest green. Round-trip is lossless (deserialize(serialize(x)) == x)
across all fields; dedup-by-hash and tier filtering asserted; **relative paths
only** invariant enforced at the model boundary (no absolute path accepted/stored).

- [x] Define `Sample` with the full field set (id, display name, relative path,
  source mode, source range in project time + PPQ, track GUID(s), wet/dry,
  channels, SR, length sec + beats, capture tempo, optional key, peak/RMS/LUFS,
  clip flag, tier, content hash, provenance, created ts). CONTEXT.md §Data model.
- [x] `BankIndex`: ordered collection keyed by id; add / remove / query.
- [x] Hash lookup for dedup-by-content-hash.
- [x] Tier model (scratch | archive) + tier-move + tier filtering; scratch marked
  auto-prunable.
- [x] JSON serialize/deserialize to/from `std::string`.
- [x] Tests: full-field round-trip lossless; dedup collapses equal-hash adds;
  tier filter/move correct; relative-path invariant rejects absolute paths;
  empty-index and malformed-JSON edge cases.

---

## Milestone 2 — peaks (pure)
**Goal:** Compute waveform min/max bins from raw PCM, dependency-free (not
REAPER's peak API). CONTEXT.md §Module architecture, §Non-goals.
**Verify:** CTest green. Fed a known signal (full-scale sine, ramp), asserted
min/max envelope per bin matches expected within tolerance; channel count
preserved; bin count honored for arbitrary sample lengths (incl. remainder bin).

- [x] Min/max bin computation from interleaved PCM given a target bin count.
- [x] Multi-channel handling (per-channel envelope; no silent fold).
- [x] Tests: sine envelope ≈ ±amplitude; ramp envelope monotonic; DC/silence →
  zero envelope; short-buffer and non-divisible-length edge cases.

---

## Milestone 3 — Offline capture spike (REAPER shell)
**Goal:** Offline-render the time-selection master mix to a wav in the project
bank folder, add a `Sample`, log it. The render-driving spike. CONTEXT.md
§REAPER API surface (offline render), Build order 3.
**Verify (in DAW):** Render runs via `Main_OnCommand(42230)` ("Render using most
recent settings") — REAPER always shows its offline-render progress window; no
stock/header-documented fully-headless path exists. File lands in the
project-relative bank folder at **32-bit float WAV** at project rate (lossless,
dither-free → enables bit-identical/null-test). A `Sample` is added to the
in-memory `BankIndex`. Non-destructive. Unsaved-project state triggers a
Save-As prompt; capture is refused if the user cancels (no default-location
fallback).
**Bit-identical repeats:** two identical requests produce byte-identical files.
**Exact bounds:** rendered length matches the requested range (no rounding, no
added silence without an explicit tail).

- [x] `ICaptureBackend` interface + `CaptureRequest` (source mode, time range,
  wet/dry, tail, SR/bit-depth/channels, output path). CONTEXT.md §capture.
- [x] `OfflineRenderBackend`: drive `GetSetProjectInfo` render settings +
  `GetSetProjectInfo_String` file/pattern/format; **verify every flag against
  `vendor/reaper-sdk/sdk/reaper_plugin_functions.h`.**
- [x] Resolve the no-dialog render command/flag on the current REAPER build
  (open question) and confirm it runs headless.
- [x] Populate a `Sample` from the finished file; hand to `bank_model`; console-log.
- [x] Verify bit-identical repeats and exact-bounds by hand on a known range.

---

## Milestone 4 — persist (index ↔ project ext state)
**Goal:** Write the `BankIndex` JSON to project ext state, reload on project open;
project-relative path resolution. CONTEXT.md §persist, §Persistence & paths.
**Verify (in DAW):** Index survives Save / Save As / close+reopen; **bank travels
with the .rpp**; **relative paths only** in the persisted index (Save As to a new
folder still resolves the bank).

- [x] `SetProjExtState` / `GetProjExtState` under namespace `"reasampler"`.
- [x] Bank-folder resolution from the current project path
  (`EnumProjects` / `GetProjectPathEx`); store under a project-relative subfolder.
- [x] Reload-on-open; confirm survival across Save / Save As.

**Notes/decisions:**
- Storage: `SetProjExtState` / `GetProjExtState`, namespace `"reasampler"`, keys `bank_index` (serialized JSON) and `project_guid`; relative paths only in the persisted index.
- Project identity: keyed off a **minted GUID** stored in ext state (REAPER exposes no native per-project GUID), not the raw `ReaProject*` — a recycled pointer cannot misread a project switch as a Save-As.
- Save-As: **copy** semantics (Daniel's decision) — the `reasampler_bank/` folder is copied under the new `.rpp`; the old project's bank stays intact. Every ext-state write calls `MarkProjectDirty` so captures/GUID changes flush on the normal save.
- Save-As collision — fixed (DAW-verified): project identity is **GUID-primary** — the stored per-project GUID is the identity of record; a different stored GUID always means a different project (Load its bank), immune to REAPER recycling `ReaProject*` addresses across close/open. The `ReaProject*` pointer is a secondary signal that disambiguates the same-GUID case only: a different object with the same GUID = a Save-As fork (Load + re-GUID to diverge); the same object with the same GUID + a new path = a genuine Save-As in progress (relocate bank). This replaced two earlier iterations: GUID-only (mis-detected forks sharing a copied GUID) and pointer-primary (mis-detected reopen/new-project because it ignored the GUID on address recycling). Non-destructive preserved.

---

## Milestone 5 — bank_panel (docked grid)
**Goal:** Docked LICE-drawn grid: thumbnails (from `peaks`), audition,
multi-select, keyboard navigation. Reuses the docking setup from the retired
`mpe_view.cpp`. CONTEXT.md §bank_panel.
**Verify (in DAW):** Grid docks; thumbnails render from computed peaks; audition
plays selected sample; multi-select + keyboard nav work.

- [x] Docked window + LICE grid render loop.
- [x] Thumbnail draw from `peaks` bins.
- [x] Audition (play selected sample) + stop.
- [x] Multi-select + keyboard navigation.

**Notes/decisions:**
- Thumbnail cache: in-memory recompute keyed by `(sampleId, drawWidth, bankGeneration)`; peak bins are NOT persisted alongside the index. Cache is discarded on bank change and rebuilt on next draw. (Closes the PLAN "thumbnail cache" open question.)
- Audition: stock `PlayPreview` / `StopPreview` API, read-only — display + select + audition only, never inserts into the arrange. Single stop-funnel ensures a leak-free preview lifecycle. Flagged undocumented assumption: `StopPreview` detaches the source before returning; mitigated by the single-funnel design. Escalation path if a runtime pop appears: switch to `StartPreviewFade` + deferred free.

---

## Milestone 6 — insert (placement)
**Goal:** "Insert selected sample at edit cursor" via `InsertMedia`. CONTEXT.md
§insert, Build order 6.
**Verify (in DAW):** Selected sample inserts at the edit cursor wrapped in
`Undo_BeginBlock2` / `Undo_EndBlock2`; conform-to-tempo is an explicit flag —
**no silent time-stretch** when off.

- [x] `InsertMedia(path, mode)` at edit cursor (verify mode bits against SDK).
- [x] Conform-to-project-tempo vs literal as an explicit flag (never silent).
- [x] Undo-block wrapping.

**Notes/decisions:**
- Placement target: inserts the focused bank sample onto the **currently selected track(s) at the edit cursor** (Daniel's directive — not a new track). Uses `InsertMedia` base mode 0; for multiple selected tracks the sample is placed on each at the same cursor position, then the original track selection and edit-cursor position are restored — non-destructive to editing state. The entire operation is one undo block.
- No silent time-stretch: the `&4` stretch-to-time-selection bit is never set; a pure `insert_plan` test asserts this across all mode combinations. Conform-to-project-tempo is an explicit separate action (`&8`), never on the default path.
- Non-destructive to the bank: insert only adds arrange items — no bank/file/ext-state writes.

---

## D1 — view_mode_model (pure)
**Goal:** REAPER-free mode registry + membership index + folder-tree-aware
visibility derivation + parking/restore planner + JSON round-trip. The heart of the
phase; mirror of `bank_model`. CONTEXT.md §Design View (Module architecture — pure).
**Verify:** CTest green. N-mode model (not a boolean); Arrange + Design seeded.
Restore-planner round-trip (snapshot → park → restore) returns every driven flag to
its captured value. Parent-derivation correct against a supplied folder tree.
JSON round-trip lossless across modes + membership + show-both + snapshots + active
mode.

- [x] Mode registry: ordered (id, display name, ordinal); Arrange + Design seeded;
  add/query more modes (prove N-mode, not binary).
- [x] Membership index: `GUID → { mode ids }` + per-track show-both flag;
  add / remove / retag / query; untagged = Arrange.
- [x] Folder-tree-aware visibility derivation: given a supplied parent↔child tree +
  active mode, compute the visible set (active leaves, derived-visible parents,
  show-both leaves, master always in).
- [x] Parking/restore planner: emit exact (track, flag, value) op-lists for park and
  restore from active mode + snapshot record.
- [x] JSON round-trip: modes + membership + show-both + snapshots + active mode.
- [x] Tests: N-mode add/query; parent follows tagged leaf (multi-mode parent);
  restore-round-trip returns snapshot values (never hardcoded "on"); show-both leaf
  never parked; unknown/stale GUID tolerated; JSON lossless.

---

## D2 — view shell (apply flags in the DAW)
**Goal:** Read the folder tree and drive REAPER flags per the planner.
CONTEXT.md §Design View (view shell, REAPER API surface).
**Verify (in DAW):** Toggling active mode hides + parks inactive leaves
(`B_SHOWINTCP`/`B_SHOWINMIXER`/`B_MAINSEND`/`I_FXEN` + per-FX offline) and restores
active ones from snapshot. **Master untouched. `B_MUTE`/`I_SOLO` untouched.**
Untagged tracks untouched. Parents follow their tagged descendants.

- [x] Build parent↔child tree from `I_FOLDERDEPTH`; feed to `view_mode_model`.
- [x] Snapshot prior flag values (`GetMediaTrackInfo_Value`) before parking.
- [x] Apply park/restore ops (`SetMediaTrackInfo_Value` for the four flags;
  `TrackFX_GetCount` + per-FX `TrackFX_SetOffline`). Verify flag names/signatures.
- [x] GUID resolution: `GetTrackGUID` / `guidToString` / `stringToGuid` (never index).
- [x] Review gate: no path touches master visibility or `B_MUTE`/`I_SOLO`, or any
  untagged track's owned flags.

---

## D3 — persist slice (view state ↔ project ext state)
**Goal:** Serialize the view section into the `"reasampler"` namespace alongside the
bank; reapply the active mode on project open. CONTEXT.md §Design View (persist).
**Verify (in DAW):** Membership + active mode + snapshots survive Save / Save As /
close+reopen; on open, the active mode's visibility + processing is reapplied.
Saved-while-parked project restores parked tracks from persisted snapshots (not to a
guessed "on").

- [x] Serialize/deserialize the view section under `"reasampler"` (shared blob,
  distinct section from the bank index).
- [x] Reapply active mode on project open (rebuild tree, run the planner).
- [x] Confirm survival across Save / Save As; snapshot durability across
  save-while-parked.

---

## D4 — actions
**Goal:** Bindable action set for the mode workflow. CONTEXT.md §Design View
(actions). **Verify (in DAW):** Each action registered (bindable in Actions list);
toggle + mode-jumps MIDI-bindable; tag/untag acts on the current track selection.

- [x] Toggle active mode (cycle; extensible to cycle-all for >2 modes).
- [x] Activate mode: Arrange / Activate mode: Design (direct jumps).
- [x] Tag selected tracks → Design / → Arrange; Untag selected (= → Arrange).
- [x] Show-both for selected tracks (toggle).
- [x] Register each (`command_id`/`gaccel`/`hookcommand`); toggle + jumps MIDI-bindable.

**Notes/decisions:**
- New `src/actions.{h,cpp}` — the Design View action family registered via the
  `command_id`/`gaccel`/`hookcommand` contract in `main.cpp`; MIDI-bindable.
- New `src/track_guid.{h,cpp}` — shared `MediaTrack*` → canonical GUID-string
  formatter; used by both the view shell and the actions layer (single source of
  truth for membership keys).
- Wiring: actions drive the D2 view shell and D3-persisted model; saved active mode
  is reapplied on project load via a load-signal seam in `persist` (`loadFromProject`
  raises it; `main.cpp`'s timer drains it) — `persist` stays model-only.
- A pure `nextModeId` free function added to `view_mode_model` (the N-mode cycle
  decision behind "toggle"), unit-tested in the existing `view_mode_model_tests`.

---

## D5 — in-window toggle affordance (UI)
**Goal:** The segmented mode switch in the ReaSampler / bank_panel window header.
CONTEXT.md §Design View (UI). **Verify (in DAW):** Segmented control shows current
mode (lit segment), one click flips modes via the D4 toggle action, per-mode
membership count visible, offlined-FX caveat surfaced as a tooltip.

- [x] Segmented mode switch `[ Arrange | Design ]` in the window header; active lit.
- [x] Wire the switch to the toggle/activate actions from D4.
- [x] Per-mode membership count display.
- [x] Offlined-FX re-init caveat as a tooltip on the switch.

**Notes/decisions:**
- New PURE module `src/mode_switch.{h,cpp}` — REAPER-free layout math for the
  Design View mode switch: divides a header rectangle into N equal segments (one per
  registered mode) and hit-tests a point to a segment. Unit-tested via a new
  `mode_switch_tests` CTest target. Mirror of `bank_grid`.
- `src/bank_panel.cpp` — segmented `[ Arrange | Design ]` control drawn in the panel
  header (one lit segment per registered mode, click activates that mode via
  `view::applyMode`), with the grid offset below the header.

---

## D2-W1 — view_mode_model lane extension (pure)
**Goal:** Extend D1's pure planner to item level for the two-canvas sub-phase:
lane↔mode mapping, a managed-vs-manual lane-ownership index, managed-only item-lane
ops in the toggle planner, the "which lanes may this toggle touch" query, the
auto-tag decision (manual-lane items exempt; pre-existing ⇒ Arrange), and JSON
round-trip of the lane index. REAPER-free, unit-tested; mirror of D1. CONTEXT.md
§Two-canvas sub-phase (Module architecture — pure).
**Verify:** CTest green; D1 behavior and tests unchanged.

- [x] Lane↔mode mapping: which lane maps to which mode, which `C_LANEPLAYS` value
  per mode.
- [x] Lane-ownership index: per (track GUID, lane) managed-which-mode vs manual;
  managed-only item-lane op family alongside the existing track-flag op family.
- [x] "Which lanes may this toggle touch" query (managed only) — planner emits lane
  ops for managed lanes only, never for manual lanes.
- [x] Auto-tag decision (pure): new track/item GUIDs + active mode ⇒ membership
  writes; manual-lane items exempt; pre-existing ⇒ Arrange.
- [x] JSON round-trip of the lane-ownership index.
- [x] Tests: managed/manual partition; toggle-touches-managed-only; auto-tag
  exemption for manual-lane items; JSON lossless; D1 behavior/tests unchanged.

---

## Milestone 7 — capture action family
**Goal:** Bindable capture actions for master / selected tracks / selected items /
razor area, each with wet-dry + tail options. CONTEXT.md §actions, Build order 7.
**Verify (in DAW):** Each action registered (bindable in Actions list), routes to
the offline backend, and honors wet/dry + tail. **Load-bearing principle:** none
auto-inserts into the arrange.

- [x] Source resolvers: master mix, selected tracks, selected items, razor area
  (`GetSet_LoopTimeRange`, `P_RAZOREDITS`, `CountSelectedMediaItems`, etc.).
- [x] Register each as a bindable action (`command_id`/`gaccel`/`hookcommand`).
- [x] Wet-dry + tail options per action.
- [x] Review gate: confirm no capture path touches the timeline.

**Notes/decisions:**
- Four **wet** bindable capture actions — master mix, selected tracks, selected items, razor area — registered under the `CEREBELLUM_REASAMPLER_CAPTURE_*` command-id prefix. Each routes to `OfflineRenderBackend` (RENDER_* snapshot/restore, dither/normalize off, 32-bit float), produces a `Sample`, adds it to the bank, persists, and calls `MarkProjectDirty`. The M3 spike action was retired.
- **Wet-only decision (Daniel):** REAPER offline render has no true pre-FX "dry" bit — the only wet/dry-adjacent lever (`&8192` pre-fader stems) is post-FX. Approximate-dry action variants were removed rather than ship a "dry" that isn't. `CaptureRequest.wetDry` is retained as the seam for true dry (M10).
- Pure `render_settings` module maps source mode → RENDER_SETTINGS bits and parses `P_RAZOREDITS` (union of track-audio areas), unit-tested. No capture path inserts into the arrange (load-bearing gate); non-destructive (selection/razor read-only).

**Superseded / reworked (post-landing):**
- The four wet source-mode actions (master/tracks/items/razor) were replaced by **three FX-scope actions** — `capture item`, `capture track`, `capture master` — with range (razor-else-time-selection) inferred orthogonally. This fixed the defect where item captures were rendered through the parent FX chain.
- **FX-scope semantics (initial rework):** item = item/take FX only; track = item FX + the selected track's own track FX; master = full chain. For item/track, the out-of-scope chain (ancestors + master, plus the item's own track for item scope) is neutralized during the render.
- **Master scope subsequently removed:** capture is now **two scopes — item and track only**. `CAPTURE_MASTER` and `CAPTURE_MASTER_REALTIME` are retired (to capture the master, render a track instead). The master track is still neutralized as out-of-scope chain for both item and track captures; it is a bypass target, not a capture scope. The realtime backend taps the selected track (track scope only; item realtime deferred).
- **`FxBypassGuard` (RAII):** snapshot → neutralize (FX bypassed via `I_FXEN`; gain zeroed via `D_VOL`; pan/width/pan-law/mode set to unity via `D_PAN`/`D_WIDTH`/`D_PANLAW`/`I_PANMODE`) → render → restore. Non-destructive. This guard is the reusable mechanism M8 (realtime backend) and M10 (null-test / true dry) build on.

---

## Milestone 8 — RealtimeRecordBackend
**Goal:** Realtime record behind the same `ICaptureBackend`, producing identical
bank entries. CONTEXT.md §capture (realtime), §Precision invariants.
**Verify (in DAW):** Hidden temp track taps each selected track's own post-fader
output via a `CreateTrackSend`; recorded file moves into the bank; **non-destructive**
— temp track (and its sends) removed cleanly, every snapshotted track arm, time
selection, and edit cursor restored unchanged on every terminal path.

- [x] Track-scope tap: a `CreateTrackSend(source, temp)` from each selected track
  into a hidden temp track (`B_MAINSEND=0`, hidden from TCP/mixer). The temp records
  its own post-fader output — capturing each source track's output **after its own FX
  and fader, before the parent/folder/master sums it** — chain-independent by
  construction. No `FxBypassGuard` needed or used. Multiple selected tracks sum in the
  temp track (matching offline track scope). Item realtime deferred (`UnsupportedMode`).
  No track selected → refused.
- [x] Timer-driven async state machine (`begin`/`tick`/`abort` driven by `OnTimer`,
  non-blocking — REAPER's UI stays responsive across the record). `begin()` validates,
  snapshots all state, creates the temp track, routes the tap, arms, calls
  `CSurf_OnRecord`, and **returns immediately**. `tick()` (called from `OnTimer`)
  reads the transport via `GetPlayStateEx`/`GetPlayPositionEx` scoped to the record's
  own `ReaProject*` (project-switch safe), advances the pure `advanceRecordPhase`
  state machine, and on a terminal verdict stops + finalizes/restores. `abort()` is
  the force-terminate path for shutdown and project switch.
- [x] `RealtimeCaptureState` snapshot + idempotent restore: snapshots cursor,
  time selection, and every other track's `I_RECARM`; restore() is latched
  (`restored_` flag) and safe to call from whichever terminal path fires first.
  Terminal paths: normal completion, manual stop, error, second-capture reject,
  project switch (project-scoped `OnStopButtonEx(proj_)`, never the global
  `CSurf_OnStop`), **project close** (guarded by `ValidatePtr2(nullptr, proj_,
  "ReaProject*")` — a closed project calls `dropWithoutRestore()` rather than
  touching freed pointers), and extension unload.
- [x] `Finalizing` flush-wait before file move: after the transport stops,
  `tick()` waits for the recorded file size to be positive and stable across a tick
  before calling `finalizeRecording` (file is no longer being written by REAPER's
  audio thread). A wall-clock ceiling (steady-clock, independent of the play cursor)
  bounds both the total record duration and the flush wait separately.
- [x] Move recorded source into bank: `recordedFilePath` discovers the take's source
  file from the temp track's first media item; `finalizeRecording` moves it into the
  bank folder (cross-volume fallback: copy+remove); populates a `Sample` via
  `sampleFromRecordedCapture`; clean teardown via `restore()` deletes the temp track
  (which REAPER uses to automatically remove every send routed into it).
- [x] Dialog-free; realtime is inherently non-deterministic (documented, not asserted
  bit-identical); saved-project gate (refuses + prompts Save-As if unsaved, matching
  offline). Bindable **cancel** action registered. Master scope removed entirely —
  to capture the master, render a track.

**Notes/decisions:**
- **Track scope only this increment.** Item realtime is deferred: item scope needs
  per-item take isolation on top of the track-output tap — a separate increment.
- **TAP vs. FxBypassGuard.** The `CreateTrackSend` defaults to post-fader
  (`I_SENDMODE=0`) with full-stereo (`I_SRCCHAN` default): post-fader taps the source
  track after its own FX and fader/pan, before the parent sums it. The parent chain
  downstream of that branch is not in the tapped path at all — so there is nothing to
  neutralize and `FxBypassGuard` (which mutates the live chain, altering the user's
  monitoring) is deliberately not used. This also fixed the earlier silent-file bug
  from the spike, which sent FROM the master INTO a temp track (a feedback loop REAPER
  refuses, recording silence). A regular track→track send has no feedback.
- **Project-close guard.** `abort()` gates every REAPER call on
  `ValidatePtr2(nullptr, proj_, "ReaProject*")`. A closed project already reclaimed
  its temp track, arms, and transport — `dropWithoutRestore()` latches `restored_`
  and clears `temp_` / `armSnaps_` without touching any REAPER pointer.
- **No undo block.** The transient mutations (temp track, sends, arm, transport) are
  fully reversed by `restore()`; surfacing them as an undo point would pollute the
  user's history with an internal scaffold they cannot meaningfully undo.

---

## T1 — offline tail: auto (default) + manual override
**Goal:** Preserve decay tails on offline captures. **Auto**: render an 8 s-capped
tail, then auto-trim trailing silence to -72 dB via a **surgical** `RENDER_NORMALIZE`
(only the trim-end bit, `32768`) + a derived `RENDER_TRIMEND` amplitude ratio.
**Manual**: a fixed tail length clamped to the 8 s cap, no trim. **None** (default):
exact bounds, byte-identical to the pre-tail capture. See
`docs/product/capture-tail.md` §The offline path.
**Verify (in DAW):** A range ending mid-reverb + Auto tail ends at the -72 dB decay
point (not a hard 8 s, not the range end); a non-decaying signal caps at range + 8 s;
**two identical Auto requests are byte-identical** (deterministic trim); a
TailMode::None capture is byte-identical to the pre-tail exact-bounds capture;
Manual(N ms) yields range + N ms untrimmed, with N clamped to 8000;
`ScopedRenderSettings` restores `RENDER_NORMALIZE` and every touched setting on every
path.

- [x] Pure layer (`render_settings.{h,cpp}`): named constants `kAutoTrimThresholdDb`
  (-72) + derived `RENDER_TRIMEND` amplitude ratio via `autoTrimEndRatio()` (≈
  0.00025119 for -72 dB, computed as `10^(dB/20)` — `std::pow` is not `constexpr`
  before C++26 so this is a function, not a constant), `kMaxTailSeconds`/`kMaxTailMs`
  (8 s); `TailMode { None, Auto, Manual }` enum; `TailRenderSettings` struct
  (tailFlag/tailMs/normalize/trimEnd); `tailRenderSettingsFor(mode, manualTailMs)`
  mapping (None = kTailFlagNone + kNormalizeDisableAll; Auto = kTailFlagCustomBounds
  + kMaxTailMs + kNormalizeTrimEnd (32768) + autoTrimEndRatio(); Manual =
  kTailFlagCustomBounds + clamped ms + kNormalizeDisableAll); unit-tested.
- [x] Wire the mapping into `OfflineRenderBackend` (`capture.cpp`): drives tail +
  surgical-normalize (Auto) / disable-all (Manual/None) via `GetSetProjectInfo`;
  `ScopedRenderSettings` snapshots and restores `RENDER_TRIMEND` alongside the
  existing `RENDER_*` set. `RENDER_TAILFLAG = kTailFlagCustomBounds` (1) for Auto
  and Manual — custom bounds is the always-applicable tail bit for offline captures.
- [x] `CaptureRequest` three-state tail contract (None/Auto/Manual(ms)); default
  None (exact bounds, null-test-safe). The earlier `renderTail` bool/`tailMs` pair
  was superseded.
- [x] Exposure: a **docked-panel footer toggle** (label "Tail: Off" / "Tail: Auto" /
  "Tail: Manual", cycles on click via `cycleTailMode`) in `bank_panel.cpp`, backed
  by the pure `tail_control` module (`TailSetting`, `cycleTailMode`,
  `clampManualMs`, `tailToggleLabel` — unit-tested). Default `TailMode::None`.
  `CAPTURE_ITEM` and `CAPTURE_TRACK` read the panel setting at fire time — **no
  per-action tail variants shipped** (the "…with tail" variants were dropped in
  favour of the toggle; null-test/verify captures use None explicitly).
- [x] DAW-confirm: `RENDER_TRIMEND` amplitude curve (0.00025119 ≈ -72 dB); trim-end-only
  normalize (32768) does not engage fades/normalize/pad; trim never eats pre-`ENDPOS`
  body. (See spec §Open questions / DAW-confirm.)

**Notes/decisions:**
- **Surgical normalize.** `kNormalizeTrimEnd = 32768` sets only the trim-ending-silence
  bit; every other postprocessing bit is clear. A fixed-threshold trailing-silence trim
  scales and fades nothing, so two identical Auto requests trim at the identical sample
  → bit-identical repeats hold (spec §surgical normalize).
- **`kNormalizeDisableAll = (4 << 16) = 262144`.** Used for None and Manual — the
  same disable-all value the pre-tail exact-bounds capture used.
- **`tail_control` pure module** (`src/tail_control.{h,cpp}`): REAPER-free logic for
  the panel toggle. `kDefaultManualTailMs = 2000.0` (2 s). Fine-adjust UI (±
  click zones / scroll) is a noted follow-on; this pass ships a fixed default.
- **Follow-ons noted, not done:** Manual fine-adjust UI; per-project persistence of
  the toggle (currently extension-session lifetime, resets to None on unload); T2
  realtime tail.