Support codex reasoning effort override

tests/test_core_flow.py

@@ -239,6 +239,7 @@ class CoreFlowTests(unittest.TestCase):
                 '\n'.join(
                     [
                         'model_provider = "ipads"',
+                        'model_reasoning_effort = "high"',
                         "",
                         "[model_providers.ipads]",
                         'base_url = "http://codex.example/v1"',
@@ -252,6 +253,7 @@ class CoreFlowTests(unittest.TestCase):
             self.assertEqual(endpoint.provider, "codex")
             self.assertEqual(endpoint.base_url, "http://codex.example/v1")
             self.assertEqual(endpoint.wire_api, "responses")
+            self.assertEqual(endpoint.reasoning_effort, "high")
             self.assertEqual(endpoint.api_key_env, "OPENAI_API_KEY")
 
     def test_extract_response_text_supports_responses_api_output(self) -> None: