The high-frequency PlaybackProgressSnapshot channel — type, mutable
snapshot, listener Set, emit/get/subscribe — moves into a dedicated
src/store/playbackProgress.ts. playerStore re-exports the public 3
(getPlaybackProgressSnapshot, subscribePlaybackProgress, the type) so
the 5+ external callers (PlayerBar, FullscreenPlayer, WaveformSeek,
LyricsPane, MobilePlayerView, TauriEventBridge) keep their existing
imports.
Direct unit tests pin the delta short-circuit (`currentTime <0.005`,
`progress/buffered <0.0002`) that keeps idle CPU bounded. The
end-to-end Tauri-event drive path remains covered by the existing
playerStore.progress characterization test (unchanged).
playerStore 3516 → 3490 LOC.
Frank Stellmacher