- Rewrote VTT translation to two-step (text-only → Gemini → apply to original timestamps) preventing caption timing desync
- Added polling fallback for all processing states and Safari visibilitychange WebSocket reconnect
- Added 11 new TTS languages (cs, da, fi, hu, no, sk, sv, es-419, pt-BR, fr-CA)
- Updated caption/AD prompts to DCMP Captioning Key & Description Key standards (line splitting, ♪ music notation, italic tags, caption positioning, ethics guidelines)
- Added descriptive transcript generation (WCAG 2.1 §1.2.1) combining captions + AD into plain text
- Fixed amix normalize=0 to prevent audio loss in rendered videos
- Fixed AD re-timing double-count when source_ms is None
- Fixed cue block numbering to be 1-based in VttEditor and Timeline Preview
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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