/**
 * DOM transition helpers for the SuperDoc collaboration upgrade.
 *
 * During `upgradeToCollaboration()`, the visible runtime is torn down and
 * rebuilt. These helpers create a frozen snapshot overlay so the user sees
 * no visual discontinuity while the new runtime initializes.
 */
/**
 * Capture the visible `.superdoc` DOM into an inert overlay before teardown.
 *
 * Returns a snapshot descriptor (overlay element + restore callback), or
 * `null` if the DOM state doesn't allow snapshotting (graceful degradation).
 *
 * @param {HTMLElement | null} container   The SuperDoc host element
 * @param {HTMLElement | null} mountWrapper The internal Vue mount wrapper
 * @returns {{ overlay: HTMLDivElement, restore: () => void } | null}
 */
export function createUpgradeSnapshot(container: HTMLElement | null, mountWrapper: HTMLElement | null): {
    overlay: HTMLDivElement;
    restore: () => void;
} | null;
/**
 * Reveal the new runtime and clean up the snapshot overlay.
 *
 * @param {HTMLElement | null} mountWrapper
 * @param {HTMLDivElement | null} overlay
 * @param {{ restore: () => void } | null} snapshot
 */
export function revealNewRuntime(mountWrapper: HTMLElement | null, overlay: HTMLDivElement | null, snapshot: {
    restore: () => void;
} | null): void;
/**
 * Emergency cleanup if an upgrade transition is aborted (e.g. by `destroy()`).
 *
 * @param {HTMLElement | null} mountWrapper
 * @param {HTMLDivElement | null} overlay
 * @param {{ restore?: () => void } | null} snapshot
 */
export function teardownUpgradeTransition(mountWrapper: HTMLElement | null, overlay: HTMLDivElement | null, snapshot: {
    restore?: () => void;
} | null): void;
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