reportMarkerPulse

Report a transient highlight ("pulse") at world location (x,y) — e.g. when a delivery completes at a drop-off point (G-animated overlay). The renderer draws an expanding, fading ring over the window [now, now + holdTime] (model time). A no-op unless the marker-pulse overlay is being captured, so models can call it unconditionally with zero cost when the overlay is off. label/colorHex are optional styling.