fix(video): improve local YouTube workflow

[caiopizzol]

Summary

• download YouTube videos through the user's signed-in browser
• return one concrete sign-in action when authenticated access is unavailable
• transcribe locally with Whisper before selecting transcript-relevant frames
• disable carried Whisper context to prevent loops in long recordings
• add audio-only, frame-only, and exact frame-time video preparation
• inspect five transcript-targeted frames, or five evenly spaced frames without usable transcript cues

Validation

• bun run check
• yt-dlp --cookies-from-browser chrome retrieved metadata for 7DRO4rEIHDk
• full local Whisper transcription with large-v3-turbo
• transcript-guided inspection of three exact frames
• context-free forward test from an isolated skill installation: authenticated download, 660 timestamped
  segments through 50:45.8, no repeated-segment pattern, and three transcript-targeted frames
• full-transcript forward test: 659 segments reviewed, five targeted frames inspected, one missed transition
  replaced
• no-audio forward test: five evenly spaced frames inspected at 0, 1.475, 2.95, 4.425, and 5.9

[cubic-dev-ai]

All reported issues were addressed across 9 files

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[cubic-dev-ai]

All reported issues were addressed across 8 files (changes from recent commits).

<sub>Tip: Review your code locally with the cubic CLI to iterate faster.

Re-trigger cubic</sub>

[cubic-dev-ai]

All reported issues were addressed across 10 files (changes from recent commits).

<sub>Tip: Review your code locally with the cubic CLI to iterate faster.
Tip: cubic used a learning from your PR history. Let your coding agent read cubic learnings directly with the cubic MCP.

Re-trigger cubic</sub>

[cubic-dev-ai]

All reported issues were addressed across 2 files (changes from recent commits).

<sub>Tip: Review your code locally with the cubic CLI to iterate faster.

Re-trigger cubic</sub>