/**
 * A still copy of an element, pinned over its place on screen.
 *
 * Wrapping an element in an html-in-canvas canvas hides it until the first
 * capture lands, one frame later. The copy covers that frame.
 *
 * - Scripts are dropped; `autoplay` is removed.
 * - `<canvas>` and `<video>` become canvases holding their current picture.
 * - `<iframe>` becomes an empty box of the same size, since a copy would load again.
 * - Form values and scroll positions are copied over.
 * - The `id` stays, so `#id` styles still apply.
 *   The page holds a duplicate id for that one frame; the copy is hidden from
 *   assistive tech and ignores the pointer.
 */
export declare function coverWithStill(element: HTMLElement, zIndex: number): () => void;