Wrap cluster test in `trio.fail_after()`

Add a 6s timeout guard around `test_streaming_to_actor_cluster()`
to catch hangs, and nest the `async with` block inside it.
Found this when running `pytest tests/ --tpt-proto uds`.

(this commit msg was generated in some part by [`claude-code`][claude-code-gh])
[claude-code-gh]: https://github.com/anthropics/claude-code

tests/test_clustering.py

@@ -56,13 +56,14 @@ async def worker(
             print(msg)
             assert msg == MESSAGE
 
-        # TODO: does this ever cause a hang
+        # ?TODO, does this ever cause a hang?
         # assert 0
 
 
 @tractor_test
-async def test_streaming_to_actor_cluster() -> None:
+async def test_streaming_to_actor_cluster():
 
+    with trio.fail_after(6):
         async with (
             open_actor_cluster(modules=[__name__]) as portals,