docs: api comments say what the endpoints do, not how they came to be (#6277)

Rewrites the internal/api comment blocks to rule 32: task, milestone and
rule ids gone, the stories behind them restated as the constraint they
left, stale references corrected (the stream secret is wired from config,
the timezone handler already refreshes the scheduler, the Android app is
the native client, the design docs cited are not in the repo). Also
rewraps comment lines over 80 columns left by the earlier batches.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/api/admin_tracks.go

@@ -10,7 +10,7 @@ import (
 	"git.fabledsword.com/bvandeusen/minstrel/internal/tracks"
 )
 
-// removeTrackResponse is the wire shape from spec §5 (M7 #372). The two
+// removeTrackResponse is DELETE /api/admin/tracks/{id}'s answer. The two
 // optional fields are omitted unless the corresponding cleanup actually
 // happened, so the response stays minimal in the common case.
 type removeTrackResponse struct {
@@ -21,9 +21,9 @@ type removeTrackResponse struct {
 
 // handleRemoveTrack implements DELETE /api/admin/tracks/{id}.
 //
-// Admin-only (gated by auth.RequireAdmin on the /admin route group). Deletes the
-// file, then the DB row, and runs the album/artist cascade tidy-up — and deletes
-// nothing at all when the file cannot be removed (#3918).
+// Admin-only (gated by auth.RequireAdmin on the /admin route group). Deletes
+// the file, then the DB row, and runs the album/artist cascade tidy-up — and
+// deletes nothing at all when the file cannot be removed.
 //
 // The codes this handler emits are not_found,
 // library_not_writable (409) and file_delete_failed when the file could not be