Per spec §10.5 — three pure functions sitting on top of the existing
useAudioStore (so React surfaces can subscribe to .unlocked if a
"click anywhere to enable audio" toast is needed later):
loadChime(file) fetch / decode arraybuffer into AudioBuffer
unlockOnFirstGesture() attach one-shot pointerdown listener that
resumes a suspended AudioContext, sets
unlocked=true. Idempotent across re-mounts
via module-level listenerAttached guard
(StrictMode double-mount safe).
playChime() → boolean returns false if the audio context isn't
ready / buffer not loaded / not unlocked,
so callers can fall back to a toast.
Phase 6 calls playChime() on alert match; Phase 5 only wires the
unlockOnFirstGesture() call into the dashboard lifecycle (Task 24)
so the audio is ready when Phase 6 lands.
CarterPerez-dev