Crossing-arrows toggle next to Play all / Play album on the playlist
detail page. When on, playQueue.start Fisher-Yates-shuffles the queue
once at start — on a copy, so the stored playlist order is untouched —
swapping per-slot album arrangements in lockstep so each slot keeps its
pinned arrangement (#685 contract preserved). Prev-less queue semantics
are unchanged: auto-advance simply walks the shuffled order.
Preference is global, persisted as localStorage v3PlaylistShuffle.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
