Metadata/art/colors delayed — currentSong, artwork, widget colors, and lyrics only updated after finalizeCrossfade. Now a songHandoff callback fires at the crossfade midpoint (50%) — updates everything mid-fade so the UI transitions with the audio. Scrobble of the outgoing song also fires here (before currentSong changes).
Visualizer stale data — Old song’s vis frames stayed in the buffer during the first half of crossfade. Now visualizerHandoff zeros offlineVisBuffer + _audioLevels before loading the new song’s data. Clean slate → simulation fills the gap → real vis takes over.
The needsNextTrack callback (post-finalize) now only handles player swap, observer re-registration, and queue persistence — no redundant metadata/scrobble work.
