Fix sub-app permissions bug, add Comments app, support Site Editor

- Root-cause fix for "Sorry, you are not allowed to access this page" on
  Menu Creator/Activity Log/Role Editor: remove_submenu_page() was
  corrupting WP core's user_can_access_admin_page() capability lookup.
  Sub-apps now stay registered in $submenu; MenuSerializer filters them
  out of the sidebar instead.
- Add a 6th sub-app, Comments, with a redirect from native edit-comments.php.
- Extend the window-chrome/taskbar framing to the Site Editor
  (site-editor.php), including a fix for a CSS position:fixed
  over-constraint bug that let its frame run past the viewport.
- Rewrite the taskbar from a single sessionStorage slot to a list so
  multiple minimized windows are each independently restorable.
- Extend native-dark.css coverage to the block editor's own chrome.

Co-Authored-By: Claude Sonnet 5 <[email protected]>

app/src/entries/comments.js

@@ -0,0 +1,10 @@
+import { createApp } from 'vue';
+import '@/shell/shell-frame.css';
+import Comments from '@/pages/comments/Comments.vue';
+
+const mountEl = document.getElementById('aurora-admin-comments-root');
+
+if (mountEl) {
+  const data = JSON.parse(mountEl.dataset.auroraAdmin || '{}');
+  createApp(Comments, { serverData: data }).mount(mountEl);
+}