fix: Fix test_configuration.py by returning config object

The test_config_loading() function was not returning the config object,
causing a NoneType error when passed to subsequent test functions.

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

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

mcp_server/tests/test_configuration.py

@@ -44,6 +44,9 @@ def test_config_loading():
     assert config is not None
     assert config2 is not None
 
+    # Return the first config for subsequent tests
+    return config
+
 
 def test_llm_factory(config: GraphitiConfig):
     """Test LLM client factory creation."""