fix: follow-up for salvaged PR #10854

- Extract duplicated activity-callback polling into shared
  touch_activity_if_due() helper in tools/environments/base.py
- Use helper from both base.py _wait_for_process and
  code_execution_tool.py local polling loop (DRY)
- Add test assertion that timeout output field contains the
  timeout message and emoji (#10807)
- Add stream_consumer test for tool-boundary fallback scenario
  where continuation is empty but final_text differs from
  visible prefix (#10807)

tests/tools/test_code_execution.py

@@ -279,6 +279,10 @@ raise RuntimeError("deliberate crash")
                 ))
         self.assertEqual(result["status"], "timeout")
         self.assertIn("timed out", result.get("error", ""))
+        # The timeout message must also appear in output so the LLM always
+        # surfaces it to the user (#10807).
+        self.assertIn("timed out", result.get("output", ""))
+        self.assertIn("\u23f0", result.get("output", ""))
 
     def test_web_search_tool(self):
         """Script calls web_search and processes results."""