Render in place: a track's output to a new sibling, source to the bench

src/shell/capture/CLAUDE.md

@@ -45,9 +45,13 @@ detail not covered there:
   `capture_realtime_shell` cannot block REAPER's UI for the duration of a realtime
   record, so `begin`/`tick`/`abort` are async by construction and the temp-track +
   send recipe lives in the shell, not the pure core.
-- **`RunInsertSelected` is the one deliberate exception to capture-never-places**
-  (see `capture_orchestrator` below) — every other capture entry point writes only
-  a file + index entry.
+- **This directory hosts TWO placing paths, and neither is a capture placing
+  itself.** `RunInsertSelected` (see `capture_orchestrator` below) places a *bank
+  sample*, on demand, which is why it is the deliberate exception to
+  capture-never-places. `render_in_place` places a render that never entered the
+  bank — the third verb (arrange → arrange, root `CLAUDE.md` §The load-bearing
+  principle). Every other entry point here writes only a file + index entry, and no
+  capture may ever grow a place step.
 
 ## Modules
 
@@ -63,6 +67,7 @@ detail not covered there:
 - `realtime_lifecycle` (`shell/capture`) — the in-flight realtime-capture state machine + globals (Q-W3 hoist): the action starts it, `OnTimer` drives it per tick via `DriveRealtimeCapture` (a single-pointer-test idle fast path — load-bearing hot-path guardrail), `CommitRealtimeResult` lands a finished capture in the bank, `AbortRealtimeCaptureForUnload` tears down cleanly on extension unload.
 - `capture_realtime_shell` (`shell/capture`) — the async realtime-record backend surface (Q-W6 split of the former fat `capture.h`): `RealtimeRecordBackend::begin`/`tick`/`abort`, transport-driven across timer ticks (a realtime record cannot block REAPER's UI for its own duration). Deliberately shares NO interface with the offline backend — the lifecycles genuinely differ (the former `ICaptureBackend` interface was deleted in Q-W3, T4-26).
 - `capture_realtime_finalize` (`shell/capture`) — the file-side half of the realtime-record shell (Q-W3, T4-08): discovers the file REAPER actually recorded, moves it into the bank, runs the Auto-tail PCM decay-scan trim, and populates the finished `Sample`.
+- `render_in_place` (`shell/capture`) — the third verb, arrange → arrange: renders the selected track's output over the resolved range through `renderOffline` with `CaptureDestination::ProjectMedia`, then places the result on a brand-new sibling track at the render window's exact start (unsnapped — this placement IS the null test performed automatically), clones the source's colour and its name through the idempotent `captureTrackName`, and settles both tracks' modes in ONE `UNDO_STATE_ALL` block. Sibling nesting comes from the pure `core/capture/track_topology::siblingPlacement`. The source is tagged Design and the result track + its items are tagged `kArrangeModeId` **explicitly and unconditionally** — never `view.activeModeId()`, and never `untag()`, because the panel's auto-tag detector defers to a membership RECORD. It reads and writes NOTHING in the bank: no `session.bank()`, no `session.book()`, no `recordCreated`, no `bumpBankGeneration`; the `Sample` the backend returns is discarded and its `relativePath` is empty by construction. Traffic is one-way — capture may borrow this render, this placement may never be borrowed back into a capture.
 - `insert` — placement via `InsertMedia`. **Conform-to-project-tempo is an explicit opt-in flag, never silent stretching.** The mono collapse needs no change here: `insert.cpp` passes only a path to `InsertMedia`, and REAPER derives the item's channel count from the file itself — a 1-channel WAV yields a mono item for free.
 - `provenance_shell` — FX-chain identity queries via `TrackFX_*`/`TakeFX_*` APIs; feeds the pure `provenance` fingerprint builder. Stamps `Sample.provenance` on capture; ambiguous/mixed cases record nothing conservatively.
 - `track_guid` — shared `MediaTrack*` → canonical GUID-string formatter; single source of truth for membership keys.