docs: record D2-W3-B landing; mark Phase D2 complete; preserve deferred panel indicator

Move D2-W3-B (item-level mode actions + W3-A polish) from PLAN.md to COMPLETED.md.
Phase D2 two-canvas sub-phase functionally complete; panel UI indicator explicitly
deferred, not dropped.

COMPLETED.md

@@ -614,3 +614,43 @@ flips to fixed-lane mode, and whether the leftover empty default lane 0 is silen
   closed with no label (discarded by REAPER) when the plan is non-empty but every write
   was already satisfied, so no phantom undo points accumulate.
 - **Review passed** with no Critical or Major findings.
+
+---
+
+## D2-W3-B — item-level mode actions + W3-A polish
+**Goal:** Item-level lane/mode-management actions mirroring the track-level Design
+View tag family (bindable in the Actions list), plus the three code-review polish
+items carried from D2-W3-A. The persist slice and lane-ownership index round-trip
+were completed in D2-W3-A; this wave closes the remaining action surface and
+cleans up the implementation.
+See CONTEXT.md §Two-canvas sub-phase (Module architecture — persistence).
+**Verify (in DAW):** Item mode actions registered and MIDI-bindable in the Actions
+list; re-drive mint/apply so each item lands on its mode's managed lane; manual-lane
+items exempt; one undo block per action. ctest 14/14 green.
+**Depends on:** D2-W3-A.
+
+- [x] "Move selected items → Design" action (`CEREBELLUM_REASAMPLER_VIEW_` family):
+  retags selected items' membership to Design mode, re-drives the existing mint/apply
+  so each item lands on its mode's managed lane; manual-lane items exempt; one undo
+  block.
+- [x] "Move selected items → Arrange" action: retags selected items' membership to
+  Arrange mode, re-drives mint/apply; manual-lane items exempt; one undo block.
+- [x] "Untag selected items" action: removes selected items' membership, re-drives
+  mint/apply; manual-lane items exempt; one undo block.
+- [x] All three registered (`command_id`/`gaccel`/`hookcommand`); MIDI-bindable.
+- [x] W3-A polish — simplified `applyMintPlan`'s redundant `I_NUMFIXEDLANES` re-read:
+  single grow-and-track pass removes the second `GetMediaTrackInfo_Value` call inside
+  the mint loop.
+- [x] W3-A polish — extracted shared item-read seam (`src/item_read.{h,cpp}`):
+  removes duplicated `itemGuid`/`itemLaneName` read logic from `view.cpp` and
+  `bank_panel.cpp`.
+- [x] W3-A polish — added reconcile guard in `reconcileManagedLanes`: skips lanes
+  encoding an unregistered mode id (log and skip rather than silently recording an
+  orphaned ownership entry).
+
+**Notes/decisions:**
+- ctest 14/14 green; review passed with no Critical or Major findings.
+- **Panel UI indicator explicitly deferred** (Daniel's decision): a per-track
+  lane-split marker has no natural cheap home in the bank panel; the mode switch
+  already shows the active mode. Preserved as a deferred/backlog note in PLAN.md
+  Phase D2 — not silently dropped.

PLAN.md

@@ -119,32 +119,14 @@ landed milestone.
 > point lands, doc-keeper moves it to `COMPLETED.md`.
 >
 > **D2-W1 (pure lane extension), D2-W2 (shell: lane application + new-content
-> detection), and D2-W3-A (lane minting + item→lane assignment + persist
+> detection), D2-W3-A (lane minting + item→lane assignment + persist round-trip),
-> round-trip) have landed** — see `COMPLETED.md`.
+> and D2-W3-B (item-level mode actions + W3-A polish) have all landed** — see
-
+> `COMPLETED.md`. **Phase D2 is functionally complete.**
-## D2-W3-B — two-canvas actions + panel UI indicators
+>
-**Goal:** Any new lane/mode-management actions (bindable in the Actions list), and
+> **Deferred:** panel UI indicator for per-track lane/mode state (a per-track
-any panel UI indicator for lane/mode state. The persist slice and the
+> lane-split marker). The mode switch already shows the active mode; no natural
-lane-ownership index round-trip were completed in D2-W3-A; this wave closes the
+> cheap home for a per-track indicator was found in the bank panel. Explicitly
-remaining UI and action surface.
+> deferred — not silently dropped. Can be picked up later if wanted.
-See CONTEXT.md §Two-canvas sub-phase (Module architecture — persistence).
-**Verify (in DAW):** Lane/mode-management actions are registered and bindable in
-the Actions list; the panel UI indicator reflects the current lane/mode state.
-**Depends on:** D2-W3-A.
-
-- [ ] Any new lane/mode-management actions (`command_id`/`gaccel`/`hookcommand`);
-  bindable in the Actions list.
-- [ ] Any panel UI indicator for lane/mode state.
-
-**D2-W3-A code-review polish (fold into this wave):**
-- [ ] Simplify the redundant per-mint `I_NUMFIXEDLANES` re-read in `view.cpp`
-  (`applyMintPlan`): a single grow-and-track pass removes the second
-  `GetMediaTrackInfo_Value` call inside the mint loop.
-- [ ] Optional shared item-read helper to remove duplicated `itemGuid`/`itemLaneName`
-  read logic between `view.cpp` and `bank_panel.cpp`.
-- [ ] Optional defensive note/check in `reconcileManagedLanes` for the edge case
-  where a managed lane name encodes an unregistered mode id (log and skip rather
-  than silently record an orphaned ownership entry).
 
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