Docs: reflect Phase D4 landing

Archive D4 (actions + integration) to COMPLETED.md; add track_guid and
Design View action family to CLAUDE.md architecture.

CLAUDE.md

@@ -59,7 +59,8 @@ There is no hot-reload. Copy the built binary into REAPER's `UserPlugins/` folde
 - `bank_panel` — docked LICE-drawn grid: thumbnails, audition, multi-select, keyboard navigation.
 - `persist` — project ext state (`SetProjExtState` / `GetProjExtState`, namespace `"reasampler"`) ↔ `bank_model` JSON + `ViewModeModel` JSON (`"view_state"` key); project-relative path resolution.
 - `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`.
-- `actions` — registers the capture/placement/slot action family and routes each to the modules above.
+- `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 and the Design View action family (toggle active mode, activate Arrange/Design, tag/untag selected tracks, show-both); routes each to the modules above via the `command_id`/`gaccel`/`hookcommand` contract.
 
 ## REAPER extension contract (src/main.cpp)