Default !similar now discovers similar artists/tracks, resolves each
against YouTube in parallel via ThreadPoolExecutor, fades out current
playback, and starts the new playlist. Old display behavior moves to
!similar list subcommand.
New helpers: _search_queries() normalizes Last.fm/MB results into search
strings, _resolve_playlist() resolves queries to _Track objects in
parallel. Falls back to display mode when music plugin not loaded.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
dd4c6b95b7