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/ghost/functional/test_content_api.py

@@ -35,10 +35,10 @@ def test_content_api_settings_endpoint(live_app):
     assert body is not None, f"GET {url} returned non-JSON body"
     # On success: {"settings": {...}}. On error: {"errors": [...]}. Either shape is valid.
     if status == 200:
-        assert isinstance(body, dict) and "settings" in body, (
-            f"200 response missing 'settings' envelope: {body!r}"
-        )
+        assert (
+            isinstance(body, dict) and "settings" in body
+        ), f"200 response missing 'settings' envelope: {body!r}"
     else:
-        assert isinstance(body, dict) and ("errors" in body or "message" in body or body), (
-            f"error response not a proper Ghost error envelope: {body!r}"
-        )
+        assert isinstance(body, dict) and (
+            "errors" in body or "message" in body or body
+        ), f"error response not a proper Ghost error envelope: {body!r}"