Priority is: CLI arg > config file > env var > default
(not env var > config file as the old comment stated)
The test failed because config.yaml had max_turns at both root level
and inside agent section. The test cleared agent.max_turns but the
root-level value still took precedence over the env var. Fixed the
test to clear both, and corrected the comment to match the intended
priority order.
afb680b50d