Adds _radioSeedId state and a module-level $effect.root that triggers a
/api/radio?seed_track=…&exclude=… fetch when queue consumption reaches
80%, appending new tracks without resetting the radio seed. Clears seed
on any non-radio enqueue (playQueue/enqueueTrack/enqueueTracks). Five
new vitest cases cover the trigger threshold, append logic, in-flight
guard, and manual-enqueue reset path.
enqueueTrack/enqueueTracks append to the queue without disturbing
playback state (no auto-play on append, no state mutation when queue
was non-empty). playRadio fetches /api/radio?seed_track=<id> and
feeds the response into playQueue. Empty response leaves queue alone.
toggleShuffle (Fisher-Yates over queue[index+1..end] with injectable
RNG for test determinism), cycleRepeat (off → all → one → off),
reportStateFromAudio with full repeat-mode semantics on 'ended',
plus simple state mirroring for playing/paused/waiting/error. Extends
skipNext to wrap when repeat='all'.
Core state (queue, index, state, position, duration, volume, shuffle,
repeat, error) plus actions: playQueue, togglePlay, linear skipNext,
skipPrev 3-second rule, seekTo, setVolume (localStorage-persisted),
registerAudioEl, reportTimeUpdate, reportDuration. Shuffle/repeat
logic and audio-event reporting land in follow-up commits.
Also install an in-memory Storage polyfill in vitest.setup.ts: Node 25
exposes a partial localStorage global that lacks getItem/setItem/clear
(requires --localstorage-file with a path), and jsdom defers to the
Node global when present, leaving tests unable to exercise storage.
bvandeusen