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/discourse/ops.py

@@ -15,8 +15,7 @@ from harness import lifecycle  # noqa: E402
 
 def _psql(domain, sql):
     cmd = (
-        'PGPASSWORD=$(cat /run/secrets/db_password) '
-        f'psql -U discourse -d discourse -tAc "{sql}"'
+        "PGPASSWORD=$(cat /run/secrets/db_password) " f'psql -U discourse -d discourse -tAc "{sql}"'
     )
     return lifecycle.exec_in_app(domain, ["sh", "-c", cmd], service="db").strip()
 
@@ -42,6 +41,7 @@ def pre_backup(domain, meta):
 def pre_restore(domain, meta):
     # diverge from the backup so a successful restore is observable
     _psql(domain, "DROP TABLE IF EXISTS ci_marker;")
-    assert _psql(domain, "SELECT to_regclass('public.ci_marker');") in ("", "NULL"), (
-        "drop did not take"
-    )
+    assert _psql(domain, "SELECT to_regclass('public.ci_marker');") in (
+        "",
+        "NULL",
+    ), "drop did not take"