fix: Clear restriction service in o3-pro test setup for proper isolation

The o3-pro test now clears the restriction service singleton in its
setup_method to ensure it re-reads environment variables set by the
@patch.dict decorator. This prevents cached restrictions from previous
tests (like test_fallback_with_shorthand_restrictions) from blocking
the o3-pro model.

This is a minimal, targeted fix that only affects the specific test
that needs it, without breaking other tests that may depend on the
restriction service state.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

tests/test_o3_pro_output_text_fix.py

@@ -41,6 +41,12 @@ class TestO3ProOutputTextFix:
         # Use the new public API for registry cleanup
         ModelProviderRegistry.reset_for_testing()
         # Provider registration is now handled by inject_transport helper
+        
+        # Clear restriction service to ensure it re-reads environment
+        # This is necessary because previous tests may have set restrictions
+        # that are cached in the singleton
+        import utils.model_restrictions
+        utils.model_restrictions._restriction_service = None
 
     def teardown_method(self):
         """Clean up after test to ensure no state pollution."""