/**
 * Traps keyboard focus within `containerRef` when `enabled` is `true`.
 *
 * Attaches a document-level `keydown` listener (via `useDocumentEvent`) and
 * intercepts `Tab` / `Shift+Tab` to keep focus cycling inside the container.
 * The listener is added/removed automatically when `enabled` changes or the
 * component unmounts.
 *
 * @param containerRef - Ref to the DOM element that should contain focus.
 * @param enabled      - Whether the trap is active. Pass `false` to disable without unmounting.
 *
 * @example
 * ```tsx
 * // Modal dialog – trap always active while open
 * useFocusTrap(contentRef, isOpen);
 *
 * // Popover – opt-in via prop
 * useFocusTrap(contentRef, isOpen && trapFocus);
 * ```
 */
export declare function useFocusTrap(containerRef: React.RefObject<HTMLElement | null>, enabled: boolean): void;