04bfb5381d
The test was picking up the real OPENAI_API_KEY from the shell
environment, causing it to fail on any machine with that key set.
Added @patch.dict(os.environ, {}, clear=True) so the test runs in
a clean env and exercises the file_env path as intended.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>