When a subagent hit max_iterations, status was always 'failed' even
if it produced a usable summary via _handle_max_iterations(). This
happened because the status check required both completed=True AND
a summary, but completed is False whenever max_iterations is reached
(run_agent.py line 7969).
Now gates status on whether a summary was produced — if the subagent
returned a final_response, the parent has usable output regardless of
iteration budget. The exit_reason field already distinguishes
'completed' vs 'max_iterations' for anything that needs to know how
the task ended.
Closes#1899.
e4d575e563