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/functional/test_site_basic.py

@@ -20,12 +20,12 @@ def test_site_json_has_discourse_config(live_app):
     status, body = harness_http.retry_http_get(
         f"https://{live_app}/site.json", expect_status=200, max_wait=120, interval=5
     )
-    assert status == 200 and isinstance(body, dict), (
-        f"GET /site.json failed: HTTP {status}, body type={type(body).__name__}"
-    )
+    assert status == 200 and isinstance(
+        body, dict
+    ), f"GET /site.json failed: HTTP {status}, body type={type(body).__name__}"
     # /site.json carries Discourse-specific structure — `categories` (a list) and `groups` are always
     # present in a booted Discourse. A non-Discourse 200 (placeholder page) would not parse to this.
     assert "categories" in body, f"/site.json missing 'categories' key: keys={list(body)[:20]}"
-    assert isinstance(body["categories"], list), (
-        f"/site.json 'categories' not a list: {type(body['categories']).__name__}"
-    )
+    assert isinstance(
+        body["categories"], list
+    ), f"/site.json 'categories' not a list: {type(body['categories']).__name__}"