feat(cli): parakeet ASR engine for transcribe + HYPERFRAMES_PYTHON override

[miguel-heygen]

Adds NVIDIA Parakeet-TDT as a hyperframes transcribe --engine parakeet|whisper|auto engine (auto = Parakeet if installed, else whisper.cpp). Beats whisper.cpp on WER + speed. Plus a HYPERFRAMES_PYTHON override for local-model python.

Stack: media-use v2 (2/5). Depends on the producer PR below.

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📚 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]

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• feat(media-use): transcription (parakeet), transcript-cut, audio-duck #1973
• 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 👈 (View in Graphite)
• fix(producer): mix muted browser media as silent for preview-render parity #1969
• main

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