✨ toggle: fx.update(tGlobal) (already called each frame by main.js) tracks
the previous tGlobal and fires on marker crossings in play AND scrub;
backward jumps and >2s forward jumps just reset the tracker. pyro/confetti ->
~1s additive particle burst at the event's resolved anchor (mapped by the
backend's label convention, stage-centroid fallback); bass_drop -> point
cloud/splat scale pulse for ~a beat (60/tempo via GET /api/beats, else 0.5s),
exact scale restored. Scene access only via scene3d.addObject/removeObject.
Hot path: 6 preallocated burst slots (160 particles each), zero per-frame
allocation, whole body behind a breaker so a throw can never kill the app
loop (it disables FX instead).
Live-verified: pyro fired at t=10.00 in play, confetti on scrub crossing 17.0,
no retro-fire on backward jump, pulse 1.16x -> exact 1.0 restore, worst-case
frame body 0.101 ms CPU (~330x inside the 30fps budget), clean toggle-off
(plan/status/lane-F.md).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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