Cluster of three small thematically-related cuts in one PR (per the new
'cluster, don't single-shot' convention):
- `src/store/seekTargetState.ts` — the seek-target guard (`seekTarget`,
`seekTargetSetAt`, `SEEK_TARGET_GUARD_TIMEOUT_MS`, set/clear/get
accessors) that suppresses stale Rust progress ticks until the
engine catches up to the requested position
- `src/store/togglePlayLock.ts` — the 300 ms double-click cooldown
behind a `tryAcquireTogglePlayLock()` helper that auto-releases on
a timer (collapses the three-line inline pattern in `togglePlay`)
- `src/store/loudnessReseed.ts` — the full `reseedLoudnessForTrackId`
pipeline (gen-bump → cache + backfill wipe → state reset → server
row delete → forced seed enqueue), pulled out of playerStore as a
single async helper
All three were file-private; no caller-side changes outside
playerStore's own imports. The progress handler's seek-guard branch is
now ~3 lines shorter and reads through accessors. `togglePlay` collapses
to one guard check.
24 tests across the three modules pin the API contracts.
playerStore 3189 → 3139 LOC.