feat(library): remove a track from the library without deleting the file

RemoveFromLibrary deletes the audio_files rows the way the scan's own
orphan cleanup does and records each path in excluded_paths. The
exclusion is not an enhancement: without it the next scan finds the
file, sees no row and imports it again, so the button undoes itself.

The soft scan compares files on disk against rows in the database, so
surveyAudioFiles and countAudioFiles both take the exclusion set —
otherwise an excluded path makes the two disagree forever and queues a
full scan on every launch. Deleting a row cascades to queue_tracks, so
the removal calls the same CompactQueue hook RemoveLibrary does.

Also lands the requested badge: library-status-indicator is a button
again where it can act, utils/library-status.ts states once what owning
and wanting mean, and the long-declared queued state finally has a
producer.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UDCbcCZQepnpSQYJ6SxxZm

frontend/src/events.ts

@@ -67,6 +67,17 @@ export const Events = {
     TrackMetadataChanged: "TrackMetadataChanged",
     BatchWriteProgress: "BatchWriteProgress",
 
+    // Track removal events.
+    //
+    // TracksRemovedFromLibrary means "these rows are gone and these paths
+    // will not be imported again", and like TrackPlayCountChanged it
+    // carries everything a consumer needs to patch rather than invalidate:
+    // {filePaths: []string, count: int}.  The library store splices those
+    // paths out of its tracks array — which is the expensive collection —
+    // and refetches only the album/artist/genre summaries, whose counts
+    // really did change
+    TracksRemovedFromLibrary: "TracksRemovedFromLibrary",
+
     // Play statistics events.
     //
     // TrackPlayCountChanged carries everything needed to patch the one