docs: document KaizenIcons as 7th design system pillar

Icon system is now the 7th pillar alongside P3 color, squircle shapes,
GlassSurface, multi-layer shadows, 4-theme system, and sensor motion.
Documents the Lucide base, custom override architecture, semantic
grouping, and how to add hand-drawn SVG overrides. Also documents the
unified top bar redesign (merged sidebar + model pill).

CLAUDE.md

@@ -47,6 +47,7 @@ settings/       SettingsScreen, SettingsViewModel, SettingsComponents, SecurityS
 ui/
   theme/        Color (P3), Theme (multi-theme), Type, Oklab, Dither
   theme/themes/ AccentScheme, AmberTheme, BlauTheme, MonoTheme, AuroraTheme, ThemeRegistry
+  icon/         KaizenIcons (central registry, Lucide base, custom override layer)
   shape/        SquircleShape (superellipse), KaizenShapes (token system)
   effect/       GlassSurface (frosted glass), Shadow (multi-layer stack)
   motion/       Motion (easing curves, spring specs, duration tokens)
@@ -65,7 +66,7 @@ ui/
 
 Full spec: `DESIGN.md`.
 
-**Six pillars** (load-bearing — if any regress, the design regresses):
+**Seven pillars** (load-bearing — if any regress, the design regresses):
 
 1. **P3 color pipeline** — all tokens in DisplayP3 color space (`Color.kt`). `window.colorMode = COLOR_MODE_HDR` (API 34+) / `COLOR_MODE_WIDE_COLOR_GAMUT` (API 26+) in `MainActivity`. No `Color(0xFF…)` for brand colors outside `Color.kt`.
 2. **Squircle shapes** — iOS-style superellipse with G2 continuity (`ui/shape/Squircle.kt`). Token system `KaizenShapes.{xs,sm,md,lg,xl,pill,circle}`. Replaces all `RoundedCornerShape`.
@@ -73,14 +74,17 @@ Full spec: `DESIGN.md`.
 4. **Multi-layer shadows** — `ShadowStack` with 2–4 overlapping layers (`KaizenShadows.level0..4`). Dark mode multiplies alphas ×1.8. Replaces all `Modifier.shadow()`.
 5. **4-theme system** — Amber/Blau/Mono/Aurora. Each theme = `KaizenAccentScheme` (primary + 4 blob colors). Neutrals are theme-independent. `LocalKaizenAccent` CompositionLocal. Theme selection wired end-to-end: `SettingsViewModel.selectedTheme` → `MainActivity` → `KaizenTheme(themeId=...)`. No server sync (web stores in localStorage, app stores locally). Appearance (Light/Dark/System) also wired end-to-end.
 6. **Sensor-reactive motion** — `rememberTiltState()` provides smoothed tilt `Offset(-1..1)`. Uses `TYPE_GAME_ROTATION_VECTOR` (fused, no drift). Auto-disables on battery saver, reduced motion, background, extreme tilt.
+7. **KaizenIcons** (`ui/icon/KaizenIcons.kt`) — centralized icon registry, same architecture as Google's Luminous Symbols. Lucide (1.5px stroke, same library as web frontend) as base, with a custom override layer for brand-critical icons. Every UI component references `KaizenIcons.Send`, `KaizenIcons.Lock`, etc. — never a library directly. Zero Material Icon imports remain. To add a custom icon: create an `ImageVector` literal (hand-drawn SVG converted to Compose path data) and swap the getter in `KaizenIcons.kt` — all usages update instantly, no call-site changes. Icons grouped semantically: Navigation, Chat, Modes, Conversation, Files, Search, Settings, Scroll. `com.composables:icons-lucide-android:1.0.0`.
 
 **Motion tokens** (`ui/motion/Motion.kt`): `EaseSpring` (overshoot), `EaseSmooth` (expo-out), `EaseEmphasized` (M3), `SpringSnappy/Default/Gentle`. All durations centralised in `Durations` object.
 
-**Migration status:** All UI components migrated to the design system. Sidebar, ChatInput, ChatScreen, LoginScreen, ModelSheet, SettingsCard, SettingsScreen use `GlassSurface` + `KaizenShapes` + `kaizenShadow`. Only Markdown code-block shapes remain as `RoundedCornerShape` (intentionally rectangular for code).
+**Migration status:** All UI components migrated to the design system. Sidebar, ChatInput, ChatScreen, LoginScreen, ModelSheet, SettingsCard, SettingsScreen use `GlassSurface` + `KaizenShapes` + `kaizenShadow` + `KaizenIcons`. Only Markdown code-block shapes remain as `RoundedCornerShape` (intentionally rectangular for code). All icons migrated from Material Icons Rounded to KaizenIcons/Lucide — zero `Icons.Rounded.*` imports remain.
 
 **Theme switching fully wired:** All 7 files that previously imported hardcoded `Amber`/`AmberDeep`/`OnAmber`/`BlobX` now read from `LocalKaizenAccent.current`. Changing theme in Settings immediately updates: message bubbles, send button, orb, mesh background blobs, sidebar highlights, model sheet, stream blocks, login screen, settings toggles. No hardcoded amber imports remain outside `Color.kt` and theme definitions.
 
-**Floating bar scrims:** Top bar (hamburger + model pill) and bottom dock (mode pills + input) have vertical gradient scrims (`MaterialTheme.colorScheme.background` → transparent) to prevent message content from bleeding through. Model pill opacity increased to 0.92.
+**Floating bar scrims:** Top bar and bottom dock have vertical gradient scrims (`MaterialTheme.colorScheme.background` → transparent) to prevent message content from bleeding through.
+
+**Unified top bar:** Sidebar trigger (menu icon) and model name merged into a single `GlassSurface` pill (38dp, `KaizenShapes.pill`). Menu icon (17dp, muted) → 3dp dot divider → model name (13sp Medium, 180dp max with ellipsis). No chevron — pill is self-evidently tappable. Matches the TokenBadge glass language on the right.
 
 **KaizenOrb** (`chat/Background.kt`) uses `rememberTiltState()` from `ui/sensor/` instead of inline sensor code. Breath animation uses `Durations.ORB_BREATH` / `ORB_BREATH_STREAMING` from `ui/motion/`.