feat: tweak calendar syncing for final release

src/plugins/built-in/timetable/calendarSyncPortal.ts

@@ -0,0 +1,16 @@
+/** Layer order: toolbar boost < menu < modal (all portaled UI uses the upper layers). */
+export const CALENDAR_SYNC_Z_MENU = 2_147_483_646;
+export const CALENDAR_SYNC_Z_MODAL = 2_147_483_647;
+
+export function portalToBody(node: HTMLElement) {
+  document.body.appendChild(node);
+  return {
+    destroy() {
+      node.remove();
+    },
+  };
+}
+
+export function isCalendarSyncModalTarget(target: EventTarget | null): boolean {
+  return target instanceof Element && Boolean(target.closest(".bsplus-cal-modal-backdrop"));
+}