palette: give the spectral mid and the envelope trace their own roles

Decouples the keyboard strip's mid stop from accent/secondary, which the
deep-teal darkening had inverted. Adds overlay/trace (#816AA6), the first
value to clear 3:1 against the waveform. Replaces the frozen-premise test.

src/core/ui/CLAUDE.md

@@ -24,23 +24,34 @@ L7 sub-pass, 2026-07-27):
 - **DS-2 — palette is role-based, not hardcoded hue**, in one constants block
   (`theme`): `bg/base`, `bg/panel`, `bg/cell`, `line/hairline`, `text/primary`,
   `text/dim`, `accent/primary`, `accent/secondary`, `accent/tertiary`,
-  `accent/hot`, `warn`. Neutral ladder sits in REAPER's mid-grey theme family
-  (`bg/base` ≈ `#2b2b2b`, `bg/panel` ≈ `#333333`, `bg/cell` ≈ `#3a3a3a`,
-  `line/hairline` ≈ `#4a4a4a`, `text/primary` ≈ `#dcdcdc`, `text/dim` ≈
+  `accent/hot`, `overlay/trace`, `warn`. Neutral ladder sits in REAPER's mid-grey
+  theme family (`bg/base` ≈ `#2b2b2b`, `bg/panel` ≈ `#333333`, `bg/cell` ≈
+  `#3a3a3a`, `line/hairline` ≈ `#4a4a4a`, `text/primary` ≈ `#dcdcdc`, `text/dim` ≈
   `~#a0a0a0`+), elevation-ladder discipline (base < panel < cell by a few %,
-  micro-gradient + inner highlight/shadow carry elevation, not hard borders).
-  Three pastel accents carry categorical meaning: **primary (pastel lime) =
-  live/active/selected**, secondary (pastel teal) + tertiary (pastel purple) =
+  micro-gradient + inner highlight/shadow carry elevation, not hard borders). The
+  accents carry categorical meaning: **primary (pastel lime) =
+  live/active/selected**, secondary (deep teal) + tertiary (pastel purple) =
   supporting categorical distinctions (kinds, not intensity). `warn` (red/amber)
   is reserved **only** for byte-deleting or clip states (prune, delete).
+  **The role count is not fixed at three** — a shade that works better in one spot
+  earns its own named role (Daniel, 2026-07-31). What does not relax: draw sites
+  ask by role. A literal color outside `theme`'s constants block is the violation,
+  not the role count.
 - **WCAG-floor discipline (tight pairs to re-verify on any palette change):**
   `text/dim` on `bg/panel`/`bg/cell` is the classic mid-grey-on-mid-grey floor
-  failure — must clear AA 4.5:1 body text. The three pastels as state
-  indicators/active fills on `bg/cell` have a shrunken contrast cushion
-  (~6:1–7:1, still clears 3:1 but re-check on any hue nudge). Body text on a
-  pastel fill is a tight AA 4.5:1 pair. Take the most pastel value that still
-  clears the floor, approached from the soft side, never re-saturated toward
-  neon "to be safe."
+  failure — must clear AA 4.5:1 body text. The accents as state indicators/active
+  fills on `bg/cell` have a shrunken contrast cushion (primary ~7.6:1, tertiary
+  ~5.5:1, secondary only ~3.9:1 since it was darkened — all still clear 3:1, but
+  re-check every one on any hue nudge). Body text on an accent fill is a tight AA
+  4.5:1 pair, and for `accent/secondary` it is the *binding* limiter (~4.9:1), not
+  the indicator floor. Take the most pastel value that still clears the floor,
+  approached from the soft side, never re-saturated toward neon "to be safe."
+- **A mark drawn OVER an accent fill answers to two neighbours at once.**
+  `overlay/trace` (the envelope trace on the waveform) must clear 3:1 against both
+  `accent/primary` and `bg/base`, which sit 9.41:1 apart — so `sqrt(9.41)` ≈ 3.07:1
+  is the ceiling for *any* single value, and the role sits at that optimum with no
+  headroom either way. It is therefore confined to the waveform band: no value can
+  clear 3:1 on `bg/cell` and against the lime simultaneously.
 - **"Speed is the selling point" — a design constraint on this geometry, not
   just the draw layer.** Sub-frame hover/press/drag feedback must repaint
   immediately on the input message. **No decorative animation** — no
@@ -68,7 +79,7 @@ L7 sub-pass, 2026-07-27):
 - `tab_strip` — REAPER-free scrollable tab-strip layout + hit-test for the named-banks strip.
 - `prune_button` — pure layout/hit-test for the `bank_panel` footer Prune button.
 - `drag_out` — pure OS drag-out module: gesture-boundary decision and path-list assembly. The `InstrumentDrop` gesture signals that the shell should execute an instrument-drop rather than a file-copy drag.
-- `theme` — pure palette module: role→color mapping, REAPER-grey neutral ladder + three-accent pastel system, WCAG contrast-floor helpers.
+- `theme` — pure palette module: role→color mapping, REAPER-grey neutral ladder + the pastel accent system, the keyboard strip's spectral ramp (its own three stops, deliberately not aliases of the accents), WCAG contrast-floor helpers.
 - `component_geometry` — pure button/slider/list-row geometry + hover hit-test helpers.
 - `action_bar` — pure task-grouped action-bar layout/hit-test: clusters (Capture / Placement / Maintenance / Tagging / Switching).
 - `footer_bar` — pure footer layout/hit-test: `[Arrange|Design]` mode-toggle geometry, Tail button, and Prune placement.

src/core/ui/theme.cpp

@@ -34,24 +34,31 @@ constexpr KitColor kDirHairline   {74, 74, 74, 255};   // #4a4a4a — subtle ste
 constexpr KitColor kDirTextPrimary{220, 220, 220, 255};  // #dcdcdc
 constexpr KitColor kDirTextDim    {168, 168, 168, 255};  // #a8a8a8 (lifted from #a0a0a0)
 
-// Three-accent pastel system: primary = pastel lime (the live/active/selected signal);
-// secondary = pastel teal, tertiary = pastel purple (CATEGORICAL distinctions — a KIND, never
-// intensity). accent/hot is a brighter tint OF the primary for hover/live/drag. On bg/cell the
-// pastels clear the 3:1 indicator floor comfortably at these values (primary ~7.6, secondary
-// ~6.8, tertiary ~5.5), so no per-hue nudge was needed. warn is reserved for byte-deleting
-// states only.
+// Accent system: primary = pastel lime (the live/active/selected signal); secondary = deep
+// teal, tertiary = pastel purple (CATEGORICAL distinctions — a KIND, never intensity).
+// accent/hot is a brighter tint OF the primary for hover/live/drag. Secondary is the one
+// accent off the pastel side: its binding limiter is the AA 4.5:1 text-on-fill pair (a bg/base
+// label on a secondary fill), NOT the 3:1 indicator floor, so it cannot go darker than this.
+// warn is reserved for byte-deleting states only.
 constexpr KitColor kDirAccentPrimary  {176, 224, 152, 255};  // #B0E098 — pastel lime
-constexpr KitColor kDirAccentSecondary{132, 214, 208, 255};  // #84D6D0 — pastel teal
+constexpr KitColor kDirAccentSecondary{56, 168, 160, 255};   // #38A8A0 — deep teal
 constexpr KitColor kDirAccentTertiary {194, 170, 232, 255};  // #C2AAE8 — pastel purple
 constexpr KitColor kDirAccentHot      {200, 236, 178, 255};  // #C8ECB2 — lighter pastel lime
 constexpr KitColor kDirWarn           {235, 120, 90, 255};   // #eb785a — destructive only
 
-// Spectral ramp: pastel lime (low) -> pastel teal (mid) -> pastel purple (high). Endpoints and
-// midpoint ARE the three accent constants (single source), so the keyboard strip reads as an
-// extension of the accent system.
-constexpr KitColor kDirSpectralLo  = kDirAccentPrimary;
-constexpr KitColor kDirSpectralMid = kDirAccentSecondary;
-constexpr KitColor kDirSpectralHi  = kDirAccentTertiary;
+// The envelope trace over the waveform. Two neighbours pin it at once — the lime accent it
+// crosses and bg/base behind it — which bound ANY single value to 3.07:1 against both; this is
+// that optimum, with no room in either direction. No categorical accent can carry it: every
+// one of them is light enough to fall under 2:1 against the lime.
+constexpr KitColor kDirOverlayTrace{129, 106, 166, 255};  // #816AA6 — muted violet
+
+// Spectral ramp: pastel lime (low) -> pastel teal (mid) -> pastel purple (high). The mid stop
+// is its OWN value rather than the secondary accent it once aliased — the ramp is a luminance
+// progression while the accents are categorical roles, and darkening secondary for a
+// categorical reason inverted lo->mid->hi. Do not re-alias it.
+constexpr KitColor kDirSpectralLo = kDirAccentPrimary;
+constexpr KitColor kDirSpectralMid{132, 214, 208, 255};  // #84D6D0 — pastel teal
+constexpr KitColor kDirSpectralHi = kDirAccentTertiary;
 
 // --- state transform helpers -------------------------------------------------
 
@@ -108,6 +115,7 @@ KitColor roleColor(Role role) {
         case Role::AccentSecondary: return kDirAccentSecondary;
         case Role::AccentTertiary:  return kDirAccentTertiary;
         case Role::AccentHot:    return kDirAccentHot;
+        case Role::OverlayTrace: return kDirOverlayTrace;
         case Role::Warn:         return kDirWarn;
     }
     return kDirBgBase;  // unreachable; keeps non-void control flow total
@@ -144,8 +152,8 @@ KitColor roleColorState(Role role, InteractionState state) {
 KitColor spectralColor(double t) {
     if (t < 0.0) t = 0.0;
     if (t > 1.0) t = 1.0;
-    // Interpolate each half separately so the midpoint IS the secondary accent (a single
-    // Lo->Hi lerp would skip it and drift the ramp off the accent family).
+    // Interpolate each half separately so the mid stop is actually hit — a single Lo->Hi lerp
+    // would skip it and drift the ramp off the pastel arc.
     if (t <= 0.5) {
         return mix(kDirSpectralLo, kDirSpectralMid, t / 0.5);
     }

src/core/ui/theme.h

@@ -1,14 +1,14 @@
 #pragma once
 // theme — the palette + type-scale core of the shared drawing kit: a ROLE-based color model
 // (bg/base, bg/panel, bg/cell, line/hairline, text/primary, text/dim, accent/primary,
-// accent/secondary, accent/tertiary, accent/hot, warn), an interaction-state model
-// (rest/hover/active/pressed/dragging/focus/disabled), and the WCAG contrast math that lets a
-// unit test prove every text-on-surface pair clears its floor.
+// accent/secondary, accent/tertiary, accent/hot, overlay/trace, warn), an interaction-state
+// model (rest/hover/active/pressed/dragging/focus/disabled), and the WCAG contrast math that
+// lets a unit test prove every text-on-surface pair clears its floor.
 //
 // Every role color is produced by roleColor() from ONE direction constants block (theme.cpp) —
 // the single point of change; no shell hardcodes a color, it asks by role. The spectral hue ramp
 // (spectralColor) lives here too so the keyboard strip derives its per-note hue from the same
-// source, anchored on the three accents (primary -> secondary -> tertiary).
+// source.
 
 #include <cstdint>
 
@@ -36,9 +36,11 @@ enum class Role {
     TextPrimary,   // labels, values
     TextDim,       // secondary / units
     AccentPrimary, // live / active / selected — where the punch lives (pastel lime)
-    AccentSecondary,// categorical role A (pastel teal) — a distinct KIND, never intensity
+    AccentSecondary,// categorical role A (deep teal) — a distinct KIND, never intensity
     AccentTertiary,// categorical role B (pastel purple) — a distinct KIND, never intensity
     AccentHot,     // hover / live / drag feedback (a brighter tint OF the primary accent)
+    OverlayTrace,  // a line/handle traced OVER an accent fill — reads against the fill AND the
+                   // surface behind it, which no accent role can do (they are all too light)
     Warn,          // clip / destructive (prune, delete) — reserved for byte-deleting states
 };
 
@@ -70,9 +72,9 @@ KitColor roleColor(Role role);
 KitColor roleColorState(Role role, InteractionState state);
 
 // Spectral hue ramp for the keyboard strip: maps normalized position t in [0, 1] (low note ->
-// high note) through accent/primary (low) -> accent/secondary (mid) -> accent/tertiary (high),
-// so the strip reads as an extension of the accent system rather than a separate flourish.
-// t is clamped to [0, 1].
+// high note) through a pastel lime -> teal -> purple arc, so the strip reads as part of the
+// palette rather than a separate flourish. The arc is its own three stops — a categorical
+// accent move must not be able to reorder it. t is clamped to [0, 1].
 KitColor spectralColor(double t);
 
 // --- WCAG contrast (the "punch" rule, made testable) --------------------------