The seat gains the events filling, full and room; at each step's end and each start the runner reads the fill of pipelines,
step-outputs, kept and step-log against their caps, says filling past 80 %, full at the cap and room below 70 %, and a start
while a store is full is refused, said in the journal and heard again by the bus.
Builds: design 47 G §366, §181
Claude-Session: https://claude.ai/code/session_01NcbgfGKaxw984XyAPfLm4h