Remove early return on missing Last.fm API key. Both commands now
fall back to MusicBrainz (mb_search_artist -> mb_artist_tags ->
mb_find_similar_recordings) when no API key is configured or when
Last.fm returns empty results. Same pattern used by discover_similar.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Every Nth autoplay pick (configurable via discover_ratio), query Last.fm
for similar tracks. When Last.fm has no key or returns nothing, fall back
to MusicBrainz tag-based recording search (no API key needed). Discovered
tracks are resolved via yt-dlp and deduplicated within the session. If
discovery fails, the kept-deck shuffle continues as before.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Covers API helpers (_get_similar_artists, _get_top_tags,
_get_similar_tracks, _search_track), config resolution, metadata
extraction from track titles, match score formatting, and both
commands (!similar, !tags) including play mode delegation, fallback
from track to artist similarity, and current-track integration.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
