Cluster of four small mutables in two modules:
- `src/store/radioSessionState.ts` — `radioFetching` (concurrent
fetch guard) + `currentRadioArtistId` (seed artist that survives
track advances) + `radioSessionSeenIds` (dedupe set including
HISTORY_KEEP-evicted entries, fixes issue #500).
- `src/store/infiniteQueueState.ts` — `infiniteQueueFetching`
concurrent fetch guard.
Sed-driven bulk rewrite for the >35 direct-access sites. The four
`= new Set()` resets become `clearRadioSessionSeenIds()` calls and
the `setRadioArtistId` / `enqueueRadio` actions read through
`getCurrentRadioArtistId()` instead of touching the mutable directly.
15 focused tests across the two modules.
playerStore 2867 → 2865 LOC.
Frank Stellmacher