fix: drain asyncssh redirect cleanup in the local ssh harness

asyncssh stores its redirect cleanup coroutines (Queue.join et al)
un-awaited and only runs them inside process.wait_closed(); the server
handler never called it, so every ssh test leaked coroutines that
pytest's unraisable hook surfaced as RuntimeWarnings during GC --
visible as stray noise in xdist runs.  Await wait_closed() in the
handler and drop the filterwarnings mark, which never covered the
GC-time warning anyway.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: RonnyPfannschmidt

testing/test_ssh_local.py

@@ -20,14 +20,9 @@
 
 import execnet
 
-pytestmark = [
-    pytest.mark.skipif(
-        shutil.which("ssh") is None, reason="system ssh client required"
-    ),
-    # asyncssh leaves an un-awaited internal Queue.join coroutine on shutdown,
-    # surfaced by pytest's unraisable-exception hook during GC; harmless here.
-    pytest.mark.filterwarnings("ignore:coroutine 'Queue.join' was never awaited"),
-]
+pytestmark = pytest.mark.skipif(
+    shutil.which("ssh") is None, reason="system ssh client required"
+)
 
 # Committed, intentionally-insecure test keys (see sshkeys/README.md).
 SSHKEYS = Path(__file__).parent / "sshkeys"
@@ -58,6 +53,10 @@ async def _handle(self, process: asyncssh.SSHServerProcess) -> None:
         )
         await process.redirect(stdin=proc.stdin, stdout=proc.stdout, stderr=proc.stderr)
         process.exit(await proc.wait())
+        # Drain asyncssh's redirect cleanup coroutines (Queue.join et al):
+        # they are stored un-awaited and only run inside wait_closed();
+        # skipping this leaks them and GC prints RuntimeWarnings.
+        await process.wait_closed()
 
     async def _serve(self) -> None:
         self._server = await asyncssh.listen(