/** Generate a UUID (native crypto with a manual fallback). */
export function generateUUID(): string;
/**
 * Stable per-device id, persisted in localStorage so it survives reloads.
 * Lazily created on first use.
 */
export function getDeviceId(): any;
/**
 * Build the default client headers for a request.
 * Empty / undetectable values are stripped so no blank headers hit the wire.
 *
 * @returns {Record<string, string>}
 */
export function buildClientHeaders(): Record<string, string>;