fix(tests): also add api_key where missing (AIAgent needs BOTH for direct path)

My last fix added base_url but not api_key. AIAgent.__init__ takes the
direct-construction path only when BOTH are set — with only base_url
it still calls resolve_provider_client and fails in hermetic CI.

Same 31 call sites, now with both kwargs.

tests/run_agent/test_create_openai_client_reuse.py

@@ -23,6 +23,7 @@ from run_agent import AIAgent
 
 def _make_agent():
     return AIAgent(
+        api_key="test-key",
         base_url="https://openrouter.ai/api/v1",
         model="test/model",
         quiet_mode=True,