incomingFromHoldsFramesAMemberSentBeforeCollection

Frames an admitted member sends before anything collects Room.incomingFrom still reach the collector that starts afterwards, in arrival order.

The ordering is forced, not raced. A probe on Room.incoming counts both frames being routed on the host and is cancelled before Room.incomingFrom is collected, so by collection time the frames have already passed through incoming. That is the host { onRoom } shape: a room admits and routes before its consumer runs. The probe count is asserted, because a probe that saw nothing would make the held-frames assertion pass for a room that simply had not routed yet.