Function waking_channel 

pub fn waking_channel<T>() -> (WakingSender<T>, Receiver<T>)

“Wake me when this worker replies”: a channel opened now, under the current wake scope (the app’s). A worker sends its replies through the WakingSender; each one wakes the app’s event loop, which drains the Receiver in its next sync. A waiting app paints nothing until a reply lands — needs_animation_frame is for motion, never for polling a worker.