Claude reports a background subagent completed when its turn ends with its own
shell still running, then resumes it with a task_started under the original
launch call while the root turn is idle. That start was only buffered as wake
evidence, so the card stayed Finished and every child frame was held behind it.
Apply that exact resume (known terminal subagent, same launch tool_use_id)
against the settled turn, keeping the subagent's own run.

The test now waits on an idle roster update as an ordered event barrier, so it
fails on the status assertion without the fix instead of reading events before
they are delivered.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>