/**
 * Shown while a map load is in flight. On a big map (~27k rooms) the load is
 * ~0.5s of parsing followed by ~1s of building the editor model and scene, all
 * synchronous on the main thread — so this exists to say *what* the frozen UI is
 * doing, and that it will finish.
 *
 * The spinner animates `transform` only (and declares `will-change`), which puts
 * it on the compositor: it keeps turning through a blocked main thread, where a
 * JS-driven or layout-driven animation would sit still. The phase label is the
 * dependable part though — each phase is committed and painted *before* its
 * blocking work starts (see `loadFile.ts`), so even if the spinner stalls on some
 * browser, the text still tells you which stage you are waiting on.
 */
export declare function MapLoadingOverlay(): import("react").JSX.Element | null;