TickSource

External ticker for driving the scheduler's task dispatch — typically a host's existing render loop (Pixi `app.ticker` , GSAP `gsap.ticker` ). The scheduler subscribes lazily: only while there are pending tasks. When the queue drains, it unsubscribes so a 60 Hz host loop isn't waking the scheduler 60 times per second to do nothing. Without a `TickSource` , the scheduler dispatches via `setTimeout` — see the "Runtime timing" guide for trade-offs around browser timer throttling and tab visibility.