style: repo-wide lint pass — make the lint gate green again

Push builds have been RED on the lint step since ~build 209 from accumulated
formatting drift. This is the mechanical cleanup: ruff format + ruff --fix
(UP038 isinstance unions, SIM105 contextlib.suppress, UP031 f-strings, SIM115
tempfile context manager), shfmt -i 2 -ci, nixpkgs-fmt/statix/deadnix (merged
attrsets, dropped unused lib args), yamllint, and shell quoting fixes in
tests/lasuite-docs/setup_custom_tests.sh. No behaviour changes intended;
lint: PASS, unit tests: 138 passed.

tests/mattermost-lts/functional/test_create_message.py

@@ -41,9 +41,9 @@ def test_create_message_roundtrip(live_app):
         headers=auth,
         timeout=30,
     )
-    assert status in (200, 201) and isinstance(team, dict) and team.get("id"), (
-        f"team creation failed: HTTP {status}, body={team!r}"
-    )
+    assert (
+        status in (200, 201) and isinstance(team, dict) and team.get("id")
+    ), f"team creation failed: HTTP {status}, body={team!r}"
     status, chan = harness_http.http_post(
         f"{base}/channels",
         data={
@@ -55,9 +55,9 @@ def test_create_message_roundtrip(live_app):
         headers=auth,
         timeout=30,
     )
-    assert status in (200, 201) and isinstance(chan, dict) and chan.get("id"), (
-        f"channel creation failed: HTTP {status}, body={chan!r}"
-    )
+    assert (
+        status in (200, 201) and isinstance(chan, dict) and chan.get("id")
+    ), f"channel creation failed: HTTP {status}, body={chan!r}"
 
     # 4) POST a unique marker message.
     marker = f"ccci-marker-{uniq}-roundtrip"
@@ -67,13 +67,13 @@ def test_create_message_roundtrip(live_app):
         headers=auth,
         timeout=30,
     )
-    assert status in (200, 201) and isinstance(post, dict) and post.get("id"), (
-        f"post creation failed: HTTP {status}, body={post!r}"
-    )
+    assert (
+        status in (200, 201) and isinstance(post, dict) and post.get("id")
+    ), f"post creation failed: HTTP {status}, body={post!r}"
 
     # 5) Read it back by id and assert the message survived the round-trip.
     status, got = harness_http.http_get(f"{base}/posts/{post['id']}", headers=auth, timeout=30)
     assert status == 200 and isinstance(got, dict), f"read-back failed: HTTP {status}, body={got!r}"
-    assert got.get("message") == marker, (
-        f"message did not round-trip: sent {marker!r}, got {got.get('message')!r}"
-    )
+    assert (
+        got.get("message") == marker
+    ), f"message did not round-trip: sent {marker!r}, got {got.get('message')!r}"