Fix 'Unknown' track artists leaking from bad ID3 tags and classical schema

- hint_extractor: filter existing tags through _is_good() so 'Unknown',
  'Unknown Artist' etc. in existing ID3 tags don't override filename-parsed
  artist names
- executor: _is_classical() now returns False when track_artist is a placeholder
  ('unknown', 'unknown artist') — prevents pop albums from getting the
  Performer-Composer-Work filename schema
- executor/music_enricher: pass albumartist to _proposed_filename() so fallback
  works when track artist is missing; fix display to use albumartist fallback too

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

music_enricher.py

@@ -97,7 +97,8 @@ def _print_proposal(proposal: AlbumProposal) -> None:
     for tp in proposal.tracks[:8]:
         tn = f"{tp.disc_number}-{tp.track_number:02d}" if tp.disc_number and tp.disc_number > 1 else (
              f"{tp.track_number:02d}" if tp.track_number else "??")
-        print(f"     {tn}  {tp.artist} – {tp.title}")
+        display_artist = tp.artist or proposal.albumartist or "Unknown"
+        print(f"     {tn}  {display_artist} – {tp.title}")
     if len(proposal.tracks) > 8:
         print(f"     … und {len(proposal.tracks) - 8} weitere")
 
@@ -156,7 +157,11 @@ def process_album(
         if args.rename:
             from executor import _proposed_filename
             for tp in proposal.tracks:
-                tp.new_filename = _proposed_filename(tp, tp.path.suffix)
+                tp.new_filename = _proposed_filename(
+                    tp, tp.path.suffix,
+                    albumartist=proposal.albumartist or "",
+                    genre=proposal.genre or "",
+                )
 
         # Review step
         if args.dry_run: