- Add _ytdlp_transcript() — fetch transcripts via yt-dlp Python API
(supports json3/srv3/vtt/srt subtitle formats, cookies.txt auth)
- Add _parse_subtitles() — parse subtitle formats into plain text
- Keep _yttranscript_api_transcript() as fallback
- download_transcript() tries yt-dlp first, then youtube-transcript-api
- Add yt-dlp to requirements.txt
- Update tests to mock both paths (all 23 pass)
- Document Google Data API v3 caption limitations in architecture.md
(captions.list works, captions.download=403 for non-owned videos)
Gan, Jimmy