A root whose 429 stop went unacknowledged waits for turn/completed. That
event finalized the root at once and cancelled the bounded wait, so a
nested turn a subagent started during the wait was never stopped and the
root terminal reported it as still running.

turn/completed now stops the active lineage before the root fails, with
the same rescan-under-permit loop the bounded wait uses, so a nested
turn either is stopped first or starts after the root is terminal.