diagnostics method
Reads permission and queue health without exposing tokens or credentials.
Implementation
Future<JackfieldDiagnostics> diagnostics() async => JackfieldDiagnostics(
mechanism: JackfieldMechanism.unavailable,
permissions: const {},
httpPausedForAuthentication: false,
lastError: const JackfieldError(JackfieldErrorCode.unsupported),
);