Client 'present' requests and cursor pokes no longer repaint on the spot:
they accumulate damage and arm a one-shot 16 ms timer, and the tick
composites everything pending as one frame. A fast mouse previously
turned every input event into a full present (100+/s); now any number of
draws and moves inside one interval coalesce into a single repaint.
No backend has a real vblank to pace by (docs/display-v2.md, 'Fenced is
not vsync'), so this is the software stand-in — the same strategy Linux
uses atop virtio-gpu. Bring-up paths that need pixels synchronously
(initialise, self-checks) still present directly.
onNotification now handles the message and timer badge bits
independently: one coalesced badge can carry both, and the old
either/or dispatch would have dropped a tick.
All six display QEMU cases pass.
Daniel Samson
4f02f75602