refactor: harden lifespan shutdown with try/finally and assert client closed in test

main.py: Wrapped `app.state.federation_client.aclose()` in a `try/finally` block so the poll task cleanup always runs even if `aclose()` raises unexpectedly.

test_api.py: Extended `test_federation_client_exists_on_app_state` to capture the client reference and assert `client_ref.is_closed` after the `TestClient` context exits, verifying the lifespan shutdown closes the client.

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Co-Authored-By: Amplifier <240397093+microsoft-amplifier@users.noreply.github.com>

muxplex/main.py

@@ -180,8 +180,9 @@ async def lifespan(app: FastAPI):
 
     yield
 
+    try:
         await app.state.federation_client.aclose()
-
+    finally:
         # Shutdown: cancel the poll loop task and wait for it to finish.
         if _poll_task is not None:
             _poll_task.cancel()

muxplex/tests/test_api.py

@@ -1464,3 +1464,10 @@ def test_federation_client_exists_on_app_state(monkeypatch):
         assert isinstance(app.state.federation_client, httpx.AsyncClient), (
             "app.state.federation_client must be an httpx.AsyncClient instance"
         )
+        # Capture reference before lifespan shuts down
+        client_ref = app.state.federation_client
+
+    # After lifespan shutdown completes, the client must be closed
+    assert client_ref.is_closed, (
+        "app.state.federation_client must be closed after lifespan shutdown"
+    )