fix(ui): unify chat composer surfaces and compact tracks

[kev1n77]

Summary

• Align badges, keyboard hints, status pills, switches, scrollbars, and launcher styling with the design system.
• Unify Composer and ChatComposer geometry, borders, shadows, and context surfaces.
• Extend Design Lab previews and preserve legacy Appearance overrides.

Type and Areas

Type: Bug fix / UI/UX

Areas: Design system, web UI, desktop appearance, Design Lab

Motivation / Impact

Compact controls had inconsistent dimensions and surface colors, while the two composer shells applied different padding and borders.

This change introduces 24px badges, 14px keyboard hints, 18px status pills, and a 72px launcher. Both composer shells now share their geometry and use a 24px compact action track with 8px padding.

Existing editor behavior, attachment queues, product controls, and footer measurement remain intact.

Verification

Recorded during implementation:

• pnpm run design-system:check — passed.
• pnpm run check:web — passed, including theme audits and TypeScript checks.
• Focused Appearance compatibility tests — 19 passed, including legacy payload round trips.
• Focused Appearance, composer, input-layout, and tail-reservation tests — 89 passed.
• Native Windows desktop: inspected the expanded composer and context band.

These checks were not rerun while preparing this PR description.

Pending manual coverage: compact indicator states, narrow layouts, live streaming, and the complete theme/density matrix.

Reviewer Notes

• Legacy Appearance field-border and surface overrides retain precedence when the new tokens are absent.
• Context blur includes reduced-transparency and forced-colors fallbacks.
• The launcher's existing Hi-to-Hello interaction is preserved.
• Generated appearance assets were refreshed through the existing generators.
• No backend protocol, persisted data shape, or viewport compensation changes.
• Remote workspace, remote control, Peer Device Mode, and Detached Dispatch were not tested end to end.

Checklist

• This PR is focused and does not include secrets, temporary prompts, generated scratch files, or unrelated artifacts.
• Relevant verification is recorded above, or skipped checks are explained.
• User-facing strings, docs, and locales are updated where applicable.