Music.app Reliability and Large Library Update

Quick update since launch. I have spent most of this week improving reliability, Music.app integration and large library support. Playback with missing local files is now cleaner and should no longer trigger repeated Locate prompts. LMO can now detect moved or replaced files more reliably even when the Persistent ID has not changed, and repaired locations are updated without rebuilding the entire library. Health Check and orphan handling were tightened to reduce the risk of importing replacement files as new Music.app records. Duplicate cleanup was also improved so verified merges no longer create automatic backup playlists, while playlist membership is still protected before removing the duplicate record. I also improved saved Library Index restore behavior for very large libraries and fixed external drive diagnostics so sandbox permissions do not produce misleading unreadable volume results. A Track Flags diagnostic also completed successfully on a test library with 827,100 Music.app records and found no abnormal playback related flags. Most of this work was about making the existing tools safer and more predictable rather than adding more features.