fix: scope PSD voiceMotion audio segments by clip instance

[ubugeeei]

Finding

voiceMotion sync appears to choose the first matching audio path. Reusing the same file in multiple clips can sync lip motion to the wrong segment.

Evidence

• src/lib/character/character-unit/psd-character.tsx voice runtime lookup.
• src/lib/sound/sound.tsx audio segment registration.

Acceptance criteria

• Key voiceMotion lookup by clip/segment identity, not only source path.
• Preserve existing single-use behavior.
• Document expected behavior for reused audio files.

[ubugeeei]

対応済みです。修正は PR #1 / commit 9cf4498 に反映済みです。