feat(media-use): transcription (parakeet), transcript-cut, audio-duck

[miguel-heygen]

Editing tools that didn't exist before: transcript-driven cutting (word-timestamp edits -> frame-accurate ffmpeg cuts), declarative auto-duck (speech spans -> GSAP volume envelope), and Parakeet-first local transcription (token->word merge, whisper.cpp fallback).

Stack: media-use v2 (5/5, top).

---

📚 Stack — media-use v2 (split from #1923, merge bottom-up)

1. fix(producer): mix muted browser media as silent for preview-render parity #1969 · producer: muted preview↔render parity
2. feat(cli): parakeet ASR engine for transcribe + HYPERFRAMES_PYTHON override #1970 · cli: Parakeet transcribe engine
3. feat(studio): non-destructive crop + cross-project asset view #1971 · studio: non-destructive crop + asset view
4. feat(media-use): v2 media OS core + retire hyperframes-media #1972 · media-use core + retire hyperframes-media
5. feat(media-use): transcription (parakeet), transcript-cut, audio-duck #1973 · media-use edit tools (transcript-cut, audio-duck, Parakeet)

[miguel-heygen]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• feat(media-use): transcription (parakeet), transcript-cut, audio-duck #1973 👈 (View in Graphite)
• feat(media-use): v2 media OS core + retire hyperframes-media #1972
• feat(studio): non-destructive crop + cross-project asset view #1971
• feat(cli): parakeet ASR engine for transcribe + HYPERFRAMES_PYTHON override #1970
• fix(producer): mix muted browser media as silent for preview-render parity #1969
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.