Extract walk()'s per-folder logic into a reusable buildFolder(), so a single
album/artist can be (re)indexed on its own. Add:
- reindexFolder(rel): rebuild just one folder's live cache entry + patch the
manifest (prune if the folder vanished). Its mtime-based signature means any
change — add / re-tag / delete — is picked up, and irrelevant touches no-op.
- withIndexLock: serialize ALL index mutations (full / incremental / localized)
so a localized reindex can never race the full reindex's atomic swap.
- watcher.ts: fs.watch(~/Music, { recursive }) → log every change → debounce 3s →
reindexFolder the affected folder(s). Verified: Bun's recursive watch fires
through the ~/Music symlink and on new-dir creation (so a new album's contents
are read by reindexFolder); inotify max_user_watches (~483k) >> folder count.
Started at boot, stopped on shutdown. The nightly full reindex backstops any
change that lands after a new folder's debounce.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
