fix(npcs): stop TipTap crash black screen in secondary windows

Guard TipTap getHTML under StrictMode, wrap secondary window roots in WindowErrorBoundary, and add stability regression tests.

Co-authored-by: Cursor <cursoragent@cursor.com>

app/renderer/editor/SceneDescriptionModal.tsx

@@ -73,7 +73,7 @@ export function SceneDescriptionModal({ initialHtml, onClose, onSave }: SceneDes
   const editor = useEditor({
     extensions,
     content: initialHtml || '',
-    immediatelyRender: true,
+    immediatelyRender: false,
     shouldRerenderOnTransaction: true,
     editorProps: {
       attributes: {
@@ -94,21 +94,56 @@ export function SceneDescriptionModal({ initialHtml, onClose, onSave }: SceneDes
   const toolbarState = useEditorState({
     editor,
     selector: ({ editor: ed }) => ({
-      bold: ed.isActive('bold'),
-      italic: ed.isActive('italic'),
-      underline: ed.isActive('underline'),
-      bulletList: ed.isActive('bulletList'),
-      orderedList: ed.isActive('orderedList'),
-      h2: ed.isActive('heading', { level: 2 }),
-      h3: ed.isActive('heading', { level: 3 }),
-      blockquote: ed.isActive('blockquote'),
+      bold: Boolean(ed && !ed.isDestroyed && ed.isActive('bold')),
+      italic: Boolean(ed && !ed.isDestroyed && ed.isActive('italic')),
+      underline: Boolean(ed && !ed.isDestroyed && ed.isActive('underline')),
+      bulletList: Boolean(ed && !ed.isDestroyed && ed.isActive('bulletList')),
+      orderedList: Boolean(ed && !ed.isDestroyed && ed.isActive('orderedList')),
+      h2: Boolean(ed && !ed.isDestroyed && ed.isActive('heading', { level: 2 })),
+      h3: Boolean(ed && !ed.isDestroyed && ed.isActive('heading', { level: 3 })),
+      blockquote: Boolean(ed && !ed.isDestroyed && ed.isActive('blockquote')),
     }),
   });
 
   const handleSave = () => {
-    onSave(normalizeSceneDescriptionHtml(editor.getHTML()));
+    if (!editor || editor.isDestroyed) return;
+    let raw = '';
+    try {
+      raw = editor.getHTML();
+    } catch {
+      return;
+    }
+    onSave(normalizeSceneDescriptionHtml(raw));
   };
 
+  if (!editor || editor.isDestroyed) {
+    return createPortal(
+      <>
+        <button
+          type="button"
+          aria-label={t('common.close')}
+          onClick={onClose}
+          className={styles.modalBackdrop}
+        />
+        <div role="dialog" aria-modal="true" className={[styles.modalDialog, modalStyles.dialog].join(' ')}>
+          <div className={styles.modalHeader}>
+            <div className={styles.modalTitle}>{t('scene.descriptionModalTitle')}</div>
+            <button
+              type="button"
+              aria-label={t('common.close')}
+              onClick={onClose}
+              className={styles.modalClose}
+            >
+              ×
+            </button>
+          </div>
+          <div className={modalStyles.editorShell} />
+        </div>
+      </>,
+      document.body,
+    );
+  }
+
   return createPortal(
     <>
       <button