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/matrix-synapse/functional/test_health_check.py

@@ -11,7 +11,6 @@ Runs in the custom tier against the shared post-install live deployment.
 
 from __future__ import annotations
 
-import json
 import os
 import sys
 
@@ -24,6 +23,6 @@ def test_synapse_client_versions_returns_json(live_app):
     url = f"https://{live_app}/_matrix/client/versions"
     status, body = harness_http.retry_http_get(url, expect_status=200, max_wait=60, interval=3)
     assert status == 200, f"GET {url} HTTP {status} (expected 200)"
-    assert isinstance(body, dict) and isinstance(body.get("versions"), list) and body["versions"], (
-        f"GET {url} did not return Matrix client-versions document: {body!r}"
-    )
+    assert (
+        isinstance(body, dict) and isinstance(body.get("versions"), list) and body["versions"]
+    ), f"GET {url} did not return Matrix client-versions document: {body!r}"