Expand description
Cocoon progress.report notification.
The git extension alone fires 6000+ of these per session. Items are
pushed into an mpsc::unbounded_channel; a single long-lived flusher
task wakes on the first item, drains everything queued, sleeps one
frame (16 ms), drains again, then emits one merged
sky://notification/progress-update per progress handle. Per-handle
merge: latest non-empty message, summed increment. Zero spawns
per call; one renderer event per handle per frame.