/**
 * Generate a UUID v4.
 *
 * This exists to avoid a hard dependency on `crypto.randomUUID()` so that
 * older supported browsers can still generate UUIDs.
 *
 * - Prefers `crypto.randomUUID()` when available.
 * - Falls back to `crypto.getRandomValues()`.
 * - Last-resort fallback uses `Math.random()` (NOT cryptographically secure).
 */
export declare function uuidV4(): string;
