docs: archive Phase L L4 to COMPLETED; reconcile CLAUDE.md + CONTEXT.md + PLAN.md

COMPLETED.md

@@ -1306,3 +1306,45 @@ button remains footer-set-apart + `warn`-colored; grid stays the centerpiece.
   kit (chrome, buttons, tabs, grid cells, dividers) by palette role with hover on
   interactive elements; remaining GDI text retired; single `KitColor→LICE_pixel` boundary
   via the kit's `toLice` (now exposed in `draw_kit.h`).
+
+---
+
+## L4 — dock-panel button layout enhancement
+**Goal:** Re-home the `bank_panel`'s L2 button inventory around *frequency and intent* —
+three-zone structure: top toolbar (capture + placement + maintenance), bottom toolbar (Design
+View tagging + switching), footer (narrow mode toggle · Tail button · Prune). A layout
+re-home of buttons that fire existing actions; no new actions, no capture/placement behavior
+change, no touching the "capture ≠ placement" principle. Independent of L3.
+CONTEXT.md §Phase L (L4 dock-panel button layout). Product framing:
+`docs/product/visual-design-language.md` §L4.
+**Verify (in DAW):** the top toolbar fires every capture + placement + maintenance action; the
+bottom toolbar tags/untags selected tracks and switches/toggles Arrange/Design/show-both; the
+footer shows a narrow `[Arrange|Design]` toggle at the left, a Tail button that cycles tail
+on click with button states, and the Prune button set apart at the right in `warn`; every
+surface draws through the L1 kit in the DS-2 grey+pastel palette; capture and placement still
+never auto-insert (the buttons only fire the existing, unchanged actions).
+
+- [x] **Top toolbar**: capture cluster (capture item, capture track, batch items, batch razor,
+  capture RT) + placement cluster (insert, insert-conform) + maintenance cluster (re-capture,
+  cancel-realtime) moved from the L2 bottom bar to a top toolbar via `action_bar` row layout;
+  buttons fire existing actions unchanged — no auto-insert.
+- [x] **Bottom toolbar**: Design View action family as buttons (tag / untag selected for mode,
+  activate Arrange, activate Design, toggle active mode, show-both) via `action_bar`
+  `ActionCluster::Tagging` + `ActionCluster::Switching`; fires existing registered Design View
+  actions.
+- [x] **Footer toggle**: `[Arrange|Design]` segmented toggle shrunk to fit-its-text width and
+  moved to the footer left of Prune; per-mode count as a compact adjacent label.
+- [x] **Footer Tail button**: Tail click-zone converted to a proper kit button (rest/hover/
+  pressed states; click still cycles the tail setting).
+- [x] **Footer order** (`[Arrange|Design]` · Tail · … · Prune `warn` set apart at the right);
+  pure footer-strip layout in new `footer_bar` module covered by CTest (`footer_bar_tests`).
+
+**Notes/decisions:**
+- **Maintenance cluster restored to top toolbar** (Daniel's directive during L4 build): the
+  initial L4 spec described the top toolbar as "capture + placement" only; the landed
+  implementation includes re-capture and cancel-realtime in a Maintenance cluster on the same
+  top toolbar. CONTEXT.md and CLAUDE.md updated to reflect the actual layout.
+- New pure module `src/footer_bar.{h,cpp}`: footer layout/hit-test (narrow mode toggle +
+  Tail button + Prune); no LICE or REAPER types. New CTest target `footer_bar_tests`.
+- `action_bar` gained `ActionCluster::Tagging` and `ActionCluster::Switching` for the
+  bottom-toolbar Design View verb groups.