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/mattermost-lts/custom/test_health_check.py

@@ -28,6 +28,6 @@ def test_system_ping_ok(live_app):
     url = f"https://{live_app}/api/v4/system/ping"
     status, body = harness_http.retry_http_get(url, expect_status=200, max_wait=120, interval=3)
     assert status == 200, f"GET {url} HTTP {status} (expected 200)"
-    assert (
-        isinstance(body, dict) and body.get("status") == "OK"
-    ), f"/api/v4/system/ping did not report status=OK; got {body!r}"
+    assert isinstance(body, dict) and body.get("status") == "OK", (
+        f"/api/v4/system/ping did not report status=OK; got {body!r}"
+    )