refactor(frontend): retire legacy CSS and isolate visual artwork

docs/client/design.md

@@ -1,7 +1,7 @@
 # Design language
 
 This guide describes the current browser UI. Use
-[legacy-theme.css](../../vocero-frontend/src/styles/legacy-theme.css) as the token/selector
+[theme.css](../../vocero-frontend/src/styles/theme.css) as the Tailwind token
 reference and [App.tsx](../../vocero-frontend/src/App.tsx) for the theme-specific structure.
 Earlier documentation described a monochrome-only dark UI; the current design
 also uses aurora gradients, glass surfaces, and a separate light theme.
@@ -10,8 +10,10 @@ also uses aurora gradients, glass surfaces, and a separate light theme.
 
 `S2S_THEME=white` selects the white/blue interface. Empty or `dark` selects the
 dark aurora interface. The browser sets `html[data-theme]` after configuration
-loads; an initial visibility guard prevents the wrong theme flashing on first
-paint. Extend the existing theme selectors when adding components.
+loads; React renders a loading screen until configuration resolves. Theme values
+live under `:root` and `html[data-theme="white"]`, with `@theme inline` exposing
+semantic utilities. The `white:` and `dark:` variants follow this attribute,
+independently of the browser's preferred color scheme.
 
 | Token group | Dark theme values/purpose |
 |---|---|
@@ -20,14 +22,20 @@ paint. Extend the existing theme selectors when adding components.
 | Text | `--text`, `--text-dim`, `--text-faint` |
 | Borders | `--border` and `--border-strong` hairlines |
 | Brand | `--brand: #8b5cf6`, `--brand-2: #ec4899`, `--brand-3: #22d3ee` |
-| Radius | `--radius-sm: 10px`, `--radius-md: 16px`, `--radius-lg: 26px`, `--radius-xl: 34px` |
+| Radius | `rounded-control: 10px`, `rounded-panel: 16px`, `rounded-card: 26px` (22px in white) |
 | Shadows | `--shadow-soft`, `--shadow-glow-brand`, `--shadow-glass` |
 
+Use semantic utilities such as `bg-surface`, `bg-surface-raised`, `text-foreground`,
+`text-muted`, `border-line`, `rounded-control` and `shadow-panel`. Palette values
+are runtime CSS variables; fonts are declared in `@theme`. Keep audio levels and
+waveform bands outside the theme token registry.
+
 Prefer existing variables and `color-mix` over new unrelated colors. The dark
 theme's orb is the strongest visual focus, while gradients and restrained role
 tints also appear in the surrounding interface. The white theme changes
 surfaces, typography contrast, controls and chat presentation through its own
-selector overrides rather than a second stylesheet.
+tokens and explicit component variants. The two voice presentations retain
+their separate React markup and scoped artwork.
 
 ## Voice state
 
@@ -62,29 +70,40 @@ details out of ordinary user flows.
 ## Layout and components
 
 The page uses a column layout: header, voice stage, always-visible inline
-conversation, and sticky footer. The conversation is no longer the old
-toggleable right overlay. Preserve space below the latest message so the sticky
-footer does not obscure it; chat autoscroll retries after layout/reflow changes.
+conversation, and footer. The document scrolls naturally while the transcript
+has its own scroll area. New messages preserve the reader's position until they
+return to the bottom or use the jump-to-latest action.
 
 In the dark theme, the reports sidebar is fixed on the left at desktop widths
-of at least 1024px. On smaller screens it becomes an off-canvas panel with a
-toggle and backdrop. The white theme hides the sidebar, its toggle, and hint.
-The user avatar opens a profile dialog; profile fields collapse from two
-columns on narrow screens. Some controls are intentionally gated by `?debug=true`.
+of at least 1024px. On smaller screens it becomes a native dialog drawer with a
+toggle and backdrop. The white theme omits the sidebar, its toggle, and hint.
+The user avatar opens a profile dialog with label/value rows. Some controls are
+intentionally gated by `?debug=true`.
+
+Reuse [ui.tsx](../../vocero-frontend/src/components/ui.tsx) for buttons, icon buttons,
+fields and dialog controls. Keep layout utilities with the owning component.
+Use complete class names in conditional maps; interpolated utility names cannot
+be detected reliably. `compact:` preserves the existing maximum width of 600px;
+`short:` covers heights at or below 640px. Other artwork breakpoints remain local.
 
-Use the existing button, icon-button, modal, switch and chat-message classes.
 The dark theme uses glass bubbles with role tints, borders and restrained glow;
-the light theme uses its white/blue message and avatar treatment. Keep required
-chat DOM elements intact; optional historical overlay controls may be absent.
+the light theme uses its white/blue message and avatar treatment.
+
+The stylesheet entry point imports Tailwind's theme and utilities without
+Preflight. Keep resets explicit in `base.css`; enabling Preflight is a separate
+visual change. Custom CSS is reserved for the page background, audio artwork,
+sanitized Markdown descendants, decorative masks and native range pseudo-elements.
+Do not add model-supplied utility classes to the Markdown sanitizer.
 
 ## Motion and accessibility
 
 Microphone RMS and assistant audio levels drive the voice visualization.
 Breathing, glow and decorative gradients should remain subordinate to speech
-feedback. `body.booting` suppresses initial transitions; new animation should
-respect that state and `prefers-reduced-motion`.
+feedback. Preserve the reduced-motion rules in `base.css`: they disable both
+CSS animations and the audio-driven transform variables. Their `!important`
+declarations intentionally override inline variables written by the audio engine.
 
-For changes, verify both themes, narrow mobile layouts down to 360px, keyboard
+For changes, verify both themes, narrow mobile layouts down to 320px, keyboard
 focus, dialog dismissal, and readable contrast. Prefer touch targets of at least
 44px and respect safe-area padding. A CSS guideline is not proof that every
 existing control already meets the target.