/**
 * Shared MutationObserver for detecting element unmount.
 *
 * One observer watches `document.body` with `subtree: true`. Each watched
 * element registers a callback; when ANY DOM removal happens, the observer
 * walks the removed subtree and fires the callback for any tracked element
 * it finds (including descendants of the actually-removed node).
 *
 * One shared observer beats per-element observers for two reasons:
 *  - parent re-mounts that detach the watched node also fire
 *  - lower memory / browser overhead than dozens of observers
 */
type UnmountCallback = () => void;
/** Register `cb` to fire when `element` is removed from the DOM. */
export declare function watchUnmount(element: HTMLElement, cb: UnmountCallback): () => void;
export {};
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