fix: add missing stream parameter to autogen_mcp run_eval fixture

Align _run() signature with other agents (react_agent, agentic_rag)
for interface consistency. The parameter defaults to False and is not
wired to TaskConfig since autogen always uses non-streaming for evals.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: andrewdonheiser

agents/autogen/mcp_agent/tests/behavioral/conftest.py

@@ -101,6 +101,7 @@ async def _run(
         timeout_seconds: float = 30.0,
         max_tokens_budget: int | None = None,
         model: str | None = None,
+        stream: bool = False,
     ) -> TaskResult:
         config = TaskConfig(
             agent_url=agent_url,