Archive Milestone 7 in docs

Move completed M7 (wet capture action family) from PLAN.md to COMPLETED.md
with a wet-only decision note; add an M10 forward note that true dry needs
FX-bypass or the realtime pre-FX path, not a render bit.

PLAN.md

@@ -14,19 +14,6 @@ it here and appends it to `COMPLETED.md`.
 
 ---
 
-## 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.
-
-- [ ] Source resolvers: master mix, selected tracks, selected items, razor area
-  (`GetSet_LoopTimeRange`, `P_RAZOREDITS`, `CountSelectedMediaItems`, etc.).
-- [ ] Register each as a bindable action (`command_id`/`gaccel`/`hookcommand`).
-- [ ] Wet-dry + tail options per action.
-- [ ] Review gate: confirm no capture path touches the timeline.
-
 ## Milestone 8 — RealtimeRecordBackend
 **Goal:** Realtime record behind the same `ICaptureBackend`, producing identical
 bank entries. CONTEXT.md §capture (realtime), §Precision invariants.
@@ -65,6 +52,8 @@ tool's trust anchor and must pass.
 - [ ] Null-test verification action (capture → re-insert at source pos → assert
   silence sum).
 
+**Note (from M7):** The null test requires a TRUE pre-FX dry capture, which REAPER offline render cannot produce via RENDER_SETTINGS (there is no pre-FX bit). True dry must be obtained by bypassing the source FX around an offline render (snapshot→bypass→render→restore) OR via the M8 realtime pre-FX path — so the dry-capture mechanism should be designed as part of the M10 null-test work.
+
 ## Milestone 11 — polish
 **Goal:** Batch capture (per selected item / per razor area),
 resample-and-mute-source, conform-on-insert, native OS drag-out. CONTEXT.md