refactor(ui): complete design system hard cutover

[GCWing]

Summary

• complete the one-step Web UI cutover from the retired component library to the public @bitfun/ui design-system contracts
• consolidate overlay, component, typography, surface, selection, and identity styling under canonical design tokens and theme ownership
• align ChatComposer actions, Harness/model controls, Global Search, navigation, settings, and generated Appearance projections with the shared system
• keep startup Appearance generation independent from the live Web UI HMR socket

Type and Areas

Type: refactor / UI/UX / regression fix / test

Areas: design system, Web UI, desktop startup Appearance projection, MiniApp Appearance projection, repository validation scripts

Motivation / Impact

This removes the dual legacy/new component path and leaves one public design-system boundary. Product surfaces now share canonical anatomy and semantic tokens, while Web UI retains product behavior and state ownership. The follow-up refinements also restore consistent compact control geometry, selected states, identity accents, and configuration layout behavior.

Verification

• pnpm run design-system:check — passed
• pnpm run check:web — passed
• pnpm exec vitest run src/app/global-search/globalSearchArchitecture.test.ts src/flow_chat/components/ChatInputWorkspaceStripLayout.test.ts src/flow_chat/components/HarnessProfileSelector.test.tsx src/infrastructure/appearance/builtins/appearancePresetOutput.test.ts src/infrastructure/appearance/builtins/startupAppearanceBootstrap.test.ts src/infrastructure/config/components/common/ConfigPageLayout.test.tsx from src/web-ui — 6 files, 68 tests passed
• node --test scripts/generate-startup-appearance-bootstrap.test.mjs — 2 tests passed
• git diff --check origin/1.0.0-explore...HEAD — passed

No browser automation, E2E, or mock visual validation was run. Remote workspace, remote control, Peer Device Mode, and Detached Dispatch were not exercised because this change does not alter their transport, runtime, or persisted contracts.

Reviewer Notes

This is an intentional hard cutover with no legacy compatibility layer. Local design/QA notes and scratch artifacts were excluded from the PR.

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.