/**
 * Returns the integer number of seconds since `startedAt` was set.
 * Pass `null` to indicate "not running" — the hook returns 0 and stops
 * the interval. Used to render "Generating try-on… 12s" labels.
 *
 * Internally ticks every 100ms so callers that need a smooth progress
 * bar can read `useElapsedFraction` (below) without re-mounting; both
 * hooks share the same underlying timer cadence so they stay in sync.
 */
export declare function useElapsedSeconds(startedAt: number | null): number;
/**
 * Returns the elapsed fractional seconds since `startedAt` was set,
 * ticking every 100ms — used by the regen button's progress bar so the
 * fill animates smoothly over its target duration instead of jumping
 * once per whole second.
 */
export declare function useElapsedFraction(startedAt: number | null): number;