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/mumble/custom/_mumble_proto.py

@@ -214,7 +214,7 @@ def handshake(
             elif msg_type == MSG_REJECT:
                 f = _dec_fields(payload)
                 result["error"] = (
-                    f"Rejected: {REJECT_TYPES.get(f.get(1, 0), 'Unknown')} " f"— {f.get(2, '')}"
+                    f"Rejected: {REJECT_TYPES.get(f.get(1, 0), 'Unknown')} — {f.get(2, '')}"
                 )
                 return result
             elif msg_type == MSG_CHANNELSTATE: