fix: revert to thread-safe queue and remove unreachable logic per review

Signed-off-by: Akshat Kumar <akshat230405@gmail.com>

Author: Akshat8510

src/google/adk/runners.py

@@ -415,7 +415,7 @@ def run(
       The events generated by the agent.
     """
     run_config = run_config or RunConfig()
-    event_queue: asyncio.Queue[Event] = asyncio.Queue()
+    event_queue: queue.Queue[Optional[Event]] = queue.Queue()
 
     async def _invoke_run_async():
       try:

tests/unittests/cli/test_fast_api.py

@@ -1414,8 +1414,8 @@ def test_builder_save_rejects_traversal(builder_test_client, tmp_path):
 
 async def _noop_run_async(*args, **kwargs):
   """A mock that does nothing and yields no events for no-op resume tests."""
-  for item in []:
-    yield item
+  if False:
+    yield
 
 
 @pytest.mark.parametrize(