v2.3.63

Fixes

• Fixes FFmpeg re-merge failures when regenerating audio or music for a video whose output path already points at the stable merged artifact.
• Writes FFmpeg merge output to a temporary same-directory file before replacing the final _with_audio.mp4 or _with_music.mp4 target.

Verification

• swift build

Fixes #64.

Full Changelog: v2.3.62...v2.3.63