reconstruction (#375)
PlaylistTrackRow.svelte and PlaylistCard.toTrackRefs both rebuilt
TrackRef from PlaylistTrack with the same field-by-field literal.
Server adding a new TrackRef field would have needed both sites
updated; now one helper owns the mapping.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>