F4: verify task recovery and document Prompt background jobs

backend/tests/test_background_task_native.py

@@ -18,6 +18,26 @@ class Passthrough(FrameProcessor):
 
 
 class NativeJobTest(unittest.IsolatedAsyncioTestCase):
+    async def test_native_timeout_calls_remote_cleanup(self):
+        cancelled = asyncio.Event()
+
+        async def execute(message, worker):
+            await asyncio.Event().wait()
+
+        async def cleanup(message):
+            cancelled.set()
+
+        async def ignore(message):
+            pass
+
+        runtime = NativeTaskRuntime(execute, cleanup, ignore, ignore)
+        await runtime.start()
+        try:
+            await runtime.submit("timeout-test", 0.05)
+            await asyncio.wait_for(cancelled.wait(), 2)
+        finally:
+            await runtime.close()
+
     async def test_progress_completion_and_media_disconnect(self):
         progress, finished, release = asyncio.Event(), asyncio.Event(), asyncio.Event()
         results = []