The authored transcript drove task_output, which no longer exists for a
continuable child and is not registered in this config, so the scenario hung.
It now demonstrates the RFC criteria directly: a delegation returning only the
durable subagent id, two send_message follow-ups queueing as later FIFO turns on
one inbox, an unknown id failing without delivery, and child-first disposal
despite a failed final durability checkpoint.
The snapshot-only overlay remaps the transcript's placeholder child id onto the
randomly minted live child, since the scripted model cannot know that id.
Also drops probe logging accidentally committed in cf0138258.