Lilac V3: live subtitle streaming + UX stabilization

[rubrot0]

Summary

• rebuild translate mode with hybrid live subtitle streaming + realtime tool-based translation
• migrate translate settings to myLanguageCode/translateToLanguageCode with legacy localStorage key migration
• add universal language catalog + custom language code support (including Ukrainian)
• simplify shell UX (compact tabs, settings surface, auto-reconnect status) and remove reconnect/clear primary controls
• improve mobile containment and composer behavior (Enter send, Shift+Enter newline)
• refresh brand contrast tokens and remove internal implementation chips from translate cards
• add dedicated transcription session action/client and update smoke assertions

Validation

• bun x biome check .
• bun run build
• bun run smoke:local
• bun run smoke:live

[vercel]

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