Fix mypy type annotation in list initialization

Author: Spchdt

src/agent/runner.py

@@ -186,7 +186,7 @@ async def _run_agent_loop(
     async def _process_event(self, event: Any) -> list[OutboundFrame]:
         """Process an ADK event and convert to OutboundFrame(s) if applicable."""
 
-        frames = []
+        frames: list[OutboundFrame] = []
         if event.interrupted:
             frames.append(
                 OutboundFrame(
@@ -226,7 +226,7 @@ async def _process_event(self, event: Any) -> list[OutboundFrame]:
 
     async def _process_content(self, content: types.Content) -> list[OutboundFrame]:
         """Process Content from an event, extracting audio/text."""
-        frames = []
+        frames: list[OutboundFrame] = []
         if not content.parts:
             return frames