fix agent stream blocking during command execution

Offload synchronous message edits from the event loop and stream subprocess output so long-running commands stay responsive.

tests/test_execute_command_tool.py

@@ -0,0 +1,57 @@
+import asyncio
+import shlex
+import sys
+import unittest
+
+import langchain.agents as langchain_agents
+
+if not hasattr(langchain_agents, "create_agent"):
+    langchain_agents.create_agent = lambda *args, **kwargs: None
+
+from app.agent.callback import StreamingHandler
+from app.agent.tools.impl.execute_command import ExecuteCommandTool
+
+
+class TestExecuteCommandTool(unittest.TestCase):
+    @staticmethod
+    def _build_python_command(script: str) -> str:
+        return f"{shlex.quote(sys.executable)} -c '{script}'"
+
+    @staticmethod
+    def _build_streaming_tool() -> tuple[ExecuteCommandTool, StreamingHandler]:
+        tool = ExecuteCommandTool(session_id="session-1", user_id="10001")
+        handler = StreamingHandler()
+        handler._streaming_enabled = True
+        handler._flush_task = object()
+        tool.set_stream_handler(handler)
+        return tool, handler
+
+    def test_run_streams_live_output_and_collects_result(self):
+        tool, handler = self._build_streaming_tool()
+        command = self._build_python_command(
+            'import sys; print("out"); print("err", file=sys.stderr)'
+        )
+
+        result = asyncio.run(tool.run(command=command, timeout=5))
+        live_output = asyncio.run(handler.take())
+
+        self.assertIn("命令执行完成 (退出码: 0)", result)
+        self.assertIn("标准输出:\nout", result)
+        self.assertIn("错误输出:\nerr", result)
+        self.assertIn("标准输出:\nout", live_output)
+        self.assertIn("错误输出:\nerr", live_output)
+
+    def test_run_timeout_keeps_partial_output(self):
+        tool = ExecuteCommandTool(session_id="session-1", user_id="10001")
+        command = self._build_python_command(
+            'import sys,time; print("start"); sys.stdout.flush(); time.sleep(0.2)'
+        )
+
+        result = asyncio.run(tool.run(command=command, timeout=0.05))
+
+        self.assertIn("命令执行超时", result)
+        self.assertIn("标准输出:\nstart", result)
+
+
+if __name__ == "__main__":
+    unittest.main()