docs: record the palette rework and retire the overlay-contrast wart it resolved

docs/COMPLETED.md

@@ -321,13 +321,16 @@ state per instance, 6 additional `DeckParam` ids.
   this reading stands.
 - **Loop markers moved from `AccentTertiary` to `AccentSecondary`** — they collided
   exactly with the envelope trace (RGB delta 0) in the same overlay rect. Daniel
-  ruled. The palette is under active change on a separate branch, so the specific hex
-  values are in flux (see `docs/TODO.md`).
+  ruled. The palette has since settled: `AccentSecondary` is `#38A8A0` (see the
+  palette-rework entry below and `src/core/ui/CLAUDE.md`).
 
-**Still open — not closed by this track.** The envelope overlay's contrast against
-the waveform (tertiary purple, measured 1.37:1, below the 3:1 indicator floor) awaits
-Daniel's eye on a build; pinned as a flagged deviation in `tests/test_theme.cpp`. See
-`docs/TODO.md`.
+**Left open by this track, resolved later.** The envelope overlay's contrast against
+the waveform (tertiary purple, measured 1.37:1, below the 3:1 indicator floor) awaited
+Daniel's eye on a build; pinned as a flagged deviation in `tests/test_theme.cpp` at the
+time. Resolved by the ad-hoc palette rework below (`91f71f9`/`a19d645`): the trace moved
+off `AccentTertiary` onto a new `Role::OverlayTrace` (`#816AA6`), clearing the floor at
+3.07:1 — the mathematical ceiling for the pairing. See the palette-rework entry below and
+`src/core/ui/CLAUDE.md`.
 
 ### Ξ-W1-T1 — tracking-consolidation
 
@@ -381,3 +384,29 @@ every beats↔seconds↔ms conversion), and `note_program` (`Velocity`, the deno
   which sees both the bytes it read and the value construction produced. `NoteProgram`
   deliberately carries no MIDI note number — render pitch is deferred to Ξ-W2 as an
   additive field.
+
+### Palette rework — accent/secondary darkening + overlay/trace role (ad-hoc, Daniel's request)
+
+Two commits (`91f71f9`, `a19d645`) resolve the envelope-overlay contrast wart Θ-W3-T2 left
+open (see above). `accent/secondary` darkened `#84D6D0` → `#38A8A0`; the keyboard strip's
+spectral mid stop decoupled from `accent/secondary` into its own constant, since the
+darkening had inverted the ramp's lo→mid→hi luminance ordering. A new `Role::OverlayTrace`
+(`#816AA6`) was added and the envelope trace + handles repointed onto it: the trace now
+measures **3.07:1** against the waveform — the mathematical ceiling for any single color
+sitting between the primary accent and `bg/base` (9.41:1 apart; `sqrt(9.41) ≈ 3.068`),
+`#816AA6` landing at 99.94% of that optimum. Two below-floor pairs remain deliberately
+accepted — the trace inside the 20%-alpha loop-span fill (2.25:1) and against the
+waveform's `line/hairline` zero-line (1.92:1) — both asserted as pinned ranges in
+`tests/test_theme.cpp` so either direction of drift fails the build.
+
+Separately: the bank panel's region title enlarged into WCAG large class via a new
+`Font::RegionTitle` (19px bold); `theme.h`'s large-text thresholds were corrected (a prior
+revision had them ~25% low, letting 15px semibold self-classify as Large); `compositeOver`
+was added to `theme` (the composited-fill arithmetic the loop-span-fill contrast pair
+depends on); and the grabbed envelope handle was repointed off hue onto a size + ring
+treatment, since no two values that clear the overlay-trace ceiling differ enough to carry
+a state by color alone.
+
+Full detail — the two-neighbour contrast rule, the WCAG threshold correction, and the
+accepted below-floor pairs — lives in `src/core/ui/CLAUDE.md` and
+`docs/product/visual-design-language.md` §4 Direction B; not duplicated here.