/**
 * Suspends workflow execution for a durable, crash-safe duration. Unlike
 * `setTimeout`, this sleep survives process restarts — the engine persists
 * the wake-up time and resumes the workflow when the timer expires.
 *
 * On replay, `sleep` returns immediately with the stored duration
 * (no actual waiting occurs). This makes it safe for deterministic
 * re-execution.
 *
 * ## Duration Formats
 *
 * Accepts any human-readable duration string parsed by the `ms` module:
 * `'5 seconds'`, `'30s'`, `'2 minutes'`, `'1m'`, `'1 hour'`, `'2h'`,
 * `'1 day'`, `'7d'`.
 *
 * ## Examples
 *
 * ```typescript
 * import { Durable } from '@hotmeshio/hotmesh';
 *
 * // Simple delay before continuing
 * export async function reminderWorkflow(userId: string): Promise<void> {
 *   const { sendReminder } = Durable.workflow.proxyActivities<typeof activities>();
 *
 *   // Wait 24 hours (survives server restarts)
 *   await Durable.workflow.sleep('24 hours');
 *   await sendReminder(userId, 'Your trial expires tomorrow');
 *
 *   // Wait another 6 days
 *   await Durable.workflow.sleep('6 days');
 *   await sendReminder(userId, 'Your trial has expired');
 * }
 * ```
 *
 * ```typescript
 * // Exponential backoff with retry loop
 * export async function pollingWorkflow(resourceId: string): Promise<string> {
 *   const { checkStatus } = Durable.workflow.proxyActivities<typeof activities>();
 *
 *   for (let attempt = 0; attempt < 10; attempt++) {
 *     const status = await checkStatus(resourceId);
 *     if (status === 'ready') return status;
 *
 *     // Exponential backoff: 1s, 2s, 4s, 8s, ...
 *     const delay = Math.pow(2, attempt);
 *     await Durable.workflow.sleep(`${delay} seconds`);
 *   }
 *   return 'timeout';
 * }
 * ```
 *
 * ```typescript
 * // Race a sleep against an activity
 * const [result, _] = await Promise.all([
 *   activities.fetchData(id),
 *   Durable.workflow.sleep('30 seconds'),
 * ]);
 * ```
 *
 * @param {string | number} duration - A human-readable duration string (e.g., `'30s'`, `'5 minutes'`) or milliseconds as a number.
 * @returns {Promise<number>} The resolved duration in seconds.
 */
export declare function sleep(duration: string | number): Promise<number>;