refactor(ui): consolidate fonts, icons, and surface controls

[GCWing]

Summary

• select Web font assets by desktop target: Apple builds use system faces, while Windows/Linux bundle audited HarmonyOS Sans and Fira Code assets with required legal notices
• remove the retired app-local iconography generator and migrate navigation/FlowChat controls to shared @bitfun/ui icon and control contracts
• refine navigation, model selection, review, session-file, and thinking surfaces while keeping Appearance and typography governance synchronized
• regenerate the MiniApp first-paint appearance projection for the updated canonical font stacks

Verification

• node --test scripts/web-font-profile.test.mjs scripts/desktop-tauri-build.test.mjs (21 passed)
• pnpm run design-system:check
• pnpm run check:web
• pnpm run build:web
• 14 focused Web Vitest files (90 passed)
• git diff --check origin/1.0.0-explore...HEAD

No browser automation, desktop E2E, or manual visual verification was performed. Remote workspace, remote control, Peer Device Mode, and Detached Dispatch were not exercised; this PR changes shared presentation assets and packaging selection rather than transport or runtime routing.