v0.5.0 - safer subtitles and flexible styling

What’s new

This release hardens subtitle generation against the real failure modes found in multi-clip Mandarin edits.

• Enables Whisper VAD and anti-hallucination decoding while preserving confidence metadata.
• Drops or clamps subtitle cues that extend beyond their source media.
• Prevents malformed per-clip subtitles from spilling into the next clip during merge.
• Writes NN.subtitle-warnings.json when suspicious cues are corrected or need review.
• Makes the per-clip cache aware of source identity and processing options.
• Adds ASS-based preview styling with bold text, normalized vertical position, global backgrounds, and black backgrounds for selected source clips.
• Adds regression coverage for the observed repeated-tail and long end-of-clip hallucinations.

New styling options

video-prep-edit ./raw \
  --subtitle-font-size 11 \
  --subtitle-bold \
  --subtitle-y 0.75 \
  --box-clips 2

Package version: 0.5.0. Skill version: 2.1.0.

Verification: 55 tests pass, including real subtitle-boundary regression cases and ASS styling tests.