lint: ruff format + one auto-fix so the push self-test is green again

`scripts/lint.sh --fix` from the pinned lint devshell: 90 Python files
reformatted (ruff format, mechanical) and one C420 (dict comprehension →
dict.fromkeys) in tests/unit/test_f211_sso_skip.py. The push self-test had
been failing at the lint stage since build 1313 (2026-08-31) on exactly
these files; nothing else changed.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FqkQq3CDmFWcQ7u1LzoyRz

tests/discourse/custom/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__}"
+    )