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/custom-html/custom/test_content_type_header.py

@@ -53,9 +53,9 @@ def test_content_type_html_and_txt(live_app):
     ct_txt = h_txt.get("content-type", "")
 
     # nginx default: "text/html" for .html and "text/plain" for .txt (may include "; charset=utf-8")
-    assert ct_html.startswith(
-        "text/html"
-    ), f"{html_name} Content-Type={ct_html!r}, expected text/html (nginx MIME config broken?)"
-    assert ct_txt.startswith(
-        "text/plain"
-    ), f"{txt_name} Content-Type={ct_txt!r}, expected text/plain (nginx MIME config broken?)"
+    assert ct_html.startswith("text/html"), (
+        f"{html_name} Content-Type={ct_html!r}, expected text/html (nginx MIME config broken?)"
+    )
+    assert ct_txt.startswith("text/plain"), (
+        f"{txt_name} Content-Type={ct_txt!r}, expected text/plain (nginx MIME config broken?)"
+    )