docs: archive Phase V (V1-V4) to COMPLETED; reconcile CLAUDE.md

Phase V landed: app_version module, ext-state version stamp, show-version
action, beta-in-isolation channel build. CLAUDE.md gains the module entry,
version key, test target, and beta-build note.

CLAUDE.md

@@ -35,8 +35,18 @@ Key targets (see CMakeLists.txt for the full list):
 | `bank_book_tests` | executable | Pure unit tests for `bank_book` — no REAPER, no DAW. |
 | `wav_trim_tests` | executable | Pure unit tests for `wav_trim` — no REAPER, no DAW. |
 | `owned_manifest_tests` | executable | Pure unit tests for `owned_manifest` — no REAPER, no DAW. |
+| `app_version_tests` | executable | Pure unit tests for `app_version` — no REAPER, no DAW. |
 | `reaper_reasampler` | loadable module | The actual extension binary (`.dll` / `.dylib` / `.so`). |
 
+### Beta channel build (Phase V, V4)
+
+To build the fully isolated beta binary (`reaper_reasampler_beta`), pass the channel flag at configure time:
+
+    cmake -B build-beta -S . -DREASAMPLER_CHANNEL=beta
+    cmake --build build-beta
+
+The flag threads through `configure_file` → `version_generated.h` and fans out via `app_version` into the binary name, ext-state namespace (`"reasampler_beta"`), command-id prefix (`CEREBELLUM_REASAMPLER_BETA_`), action-name prefix (`"ReaSampler beta: "`), dock ident, and version display (`"0.9.01-beta"`). The default build (no flag) is byte-identical to the pre-V4 stable identity.
+
 ### macOS / Linux: SWELL dialog resources
 
 `src/resource.rc` must be pre-processed by SWELL's resgen once per platform:
@@ -59,13 +69,14 @@ There is no hot-reload. Copy the built binary into REAPER's `UserPlugins/` folde
 - `mode_switch` — REAPER-free segment layout + hit-test math for the bank_panel's Design View mode switch; divides a header rectangle into N equal segments and hit-tests a point to a segment. Mirror of `bank_grid`.
 - `bank_book` — multi-bank registry (Phase B): an ordered set of banks (pool seeded as bank-zero + named banks), each wrapping a `BankIndex`. Owns create/rename/reorder/delete of named banks, pool privileges (un-deletable/un-renamable/un-evacuable, never zero banks) enforced in-model, active-bank id, index-only move/copy/remove of a sample between or from banks, `hashReferencedElsewhere` cross-bank reference query, JSON round-trip + legacy-`bank_index`→pool migration. Wraps `BankIndex` (bank_model untouched; no `bankId` on `Sample`).
 - `owned_manifest` — owned-file manifest seam (Phase B B-cap): the set of project-relative files the capture path itself created, persisted under the `"owned_files"` ext-state key, so Phase R prune can distinguish the bank system's own orphans from hand-dropped files. Deliberately decoupled from `bank_book` — tracks files created, not index membership. Phase R (R1/R2) consumes it; no prune logic here.
+- `app_version` — REAPER-free version/channel identity (Phase V, V1+V4): CMake-sourced semver constant (`appVersion()`), ext-state stamp value (`stampVersion()` — numeric triple only, no channel suffix), `parseVersion`/`versionLess`/`classifyWritingVersion`, and the full set of channel-derived identity accessors (`extStateNamespace()`, `commandIdPrefix()`, `actionDisplayPrefix()`, `binaryName()`, `dockTitle()`, `dockIdent()`, `channelCommandId()`, `channelActionName()`). All channel strings derive from the one `REASAMPLER_CHANNEL_IS_BETA` bit threaded in via `configure_file` → `version_generated.h`; no scattered `#ifdef`s in the shells.
 - `wav_trim` — 32-bit-float WAV parse + header-aware truncate plan (RIFF/data size rewrite) for the realtime tail's PCM decay-scan trim (T2). Rejects WAVE_FORMAT_EXTENSIBLE with non-float SubFormat GUID. Depends on `peaks` for the `AudioSample` float alias.
 
 **REAPER-facing shells:**
 - `capture` — `ICaptureBackend` interface; `OfflineRenderBackend` (deterministic default) and `RealtimeRecordBackend`. Input: `CaptureRequest`. Output: finished file + populated `Sample` handed to `bank_model`.
 - `insert` — placement via `InsertMedia`; conform-to-project-tempo is an explicit opt-in flag, never silent stretching.
 - `bank_panel` — docked LICE-drawn grid: thumbnails, audition, multi-select, keyboard navigation.
-- `persist` — project ext state (`SetProjExtState` / `GetProjExtState`, namespace `"reasampler"`) ↔ `BankBook` JSON (`"banks"` key) + `ViewModeModel` JSON (`"view_state"` key) + `TailSetting` JSON (`"tail_setting"` key) + `OwnedManifest` JSON (`"owned_files"` key); project-relative path resolution. A `projectconfig` hook (`BeginLoadProjectState(isUndo)`) triggers a deferred session reload on undo/redo so Ctrl-Z/redo visibly restores book/view/tail/manifest in-session.
+- `persist` — project ext state (`SetProjExtState` / `GetProjExtState`, namespace `"reasampler"`) ↔ `BankBook` JSON (`"banks"` key) + `ViewModeModel` JSON (`"view_state"` key) + `TailSetting` JSON (`"tail_setting"` key) + `OwnedManifest` JSON (`"owned_files"` key) + writing-version stamp (`"version"` key, written via `stampVersion()` on every `saveToActiveProject()`); project-relative path resolution. A `projectconfig` hook (`BeginLoadProjectState(isUndo)`) triggers a deferred session reload on undo/redo so Ctrl-Z/redo visibly restores book/view/tail/manifest in-session.
 - `view` — Design View shell: reads the folder tree via `view_tree`, snapshots flag values before parking, drives hide + CPU-park on inactive-mode leaves (`B_SHOWINTCP`/`B_SHOWINMIXER`/`B_MAINSEND`/`I_FXEN` + per-FX offline) and derived visibility on parents; restores from snapshot. Never touches master or `B_MUTE`/`I_SOLO`.
 - `track_guid` — shared `MediaTrack*` → canonical GUID-string formatter; single source of truth for membership keys used by both the view shell and the actions layer.
 - `actions` — registers the capture/placement/slot action family, the Design View action family (toggle active mode, activate Arrange/Design, tag/untag selected tracks, show-both), and the multi-bank action family (create/rename/reorder/delete bank, evacuate, activate, move/copy/remove selected samples); routes each to the modules above via the `command_id`/`gaccel`/`hookcommand` contract. Every bank index verb wraps its mutation in a batched REAPER undo point (`Undo_BeginBlock2`/`EndBlock2`, `UNDO_STATE_MISCCFG`) so one bank operation is one Ctrl-Z.
@@ -75,7 +86,7 @@ There is no hot-reload. Copy the built binary into REAPER's `UserPlugins/` folde
 - Exactly **one** translation unit defines `REAPERAPI_IMPLEMENT` — that is `main.cpp`. Every other `.cpp` includes `reaper_plugin_functions.h` without the define and gets `extern` declarations for the global API function pointers.
 - REAPER dlopen()s any `reaper_*.dll|dylib|so` found in `UserPlugins/` and calls the `ReaperPluginEntry` export (produced by `REAPER_PLUGIN_ENTRYPOINT`). `rec->GetFunc` resolves API pointers; `rec->Register` plugs extension callbacks in.
 - Action registration pattern (preserve this for all new actions):
-  1. `rec->Register("command_id", (void*)"STABLE_FOREVER_STRING")` — mints a persistent command id. **Never change this string after shipping**; user keybindings key off it.
+  1. `rec->Register("command_id", (void*)"STABLE_FOREVER_STRING")` — mints a persistent command id. **Never change this string after shipping**; user keybindings key off it. Since Phase V (V4), ids and display names are composed via `channelCommandId(suffix)` and `channelActionName(phrase)` from `app_version` — the FOREVER-STABLE contract applies per channel (stable and beta each have their own permanent id family).
   2. `rec->Register("gaccel", &accel)` — puts the action in the Actions list.
   3. `rec->Register("hookcommand", ...)` — receives every action fired; claim only your own id, return `false` otherwise.
   4. On unload (`rec == nullptr`), mirror-unregister everything with the same strings prefixed by `'-'`.