/**
 * Portal root for the app's own full-screen overlays.
 *
 * The admin stylesheet pins ``#recomaze-app-container`` to the area right of
 * the WordPress admin menu and gives it layout containment, so a
 * ``position: fixed`` overlay rendered inside it covers the app instead of the
 * whole window. An overlay portalled to ``document.body`` escapes that: it
 * spans the viewport, and the admin menu - which paints above it - hides its
 * left edge. Rect-anchored layers (tooltips, popovers) must keep portalling to
 * ``document.body``, because the coordinates they measure are viewport ones.
 *
 * @return {HTMLElement} The app shell, or ``document.body`` outside it.
 */
export function appOverlayRoot(): HTMLElement {
  return document.getElementById('recomaze-app-container') ?? document.body;
}