export function toErrorMessage(error: unknown, fallback: string): string {
  if (error && typeof error === 'object' && 'data' in error) {
    const data = (error as { data?: { message?: unknown } }).data;
    if (typeof data?.message === 'string' && data.message) {
      return data.message;
    }
  }
  if (error instanceof Error && error.message) {
    return error.message;
  }
  return fallback;
}