feat(scenes): rich scene descriptions and control viewer window

Add TipTap editing in the editor and an Electron window on the control panel to read the current scene description.

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

app/renderer/sceneDescription/SceneDescriptionApp.tsx

@@ -0,0 +1,50 @@
+import React, { useEffect, useMemo, useState } from 'react';
+
+import { ipcChannels } from '../../shared/ipc/contracts';
+import { useEditorI18n } from '../editor/i18n/EditorI18nContext';
+import { isSceneDescriptionEmpty, sanitizeSceneDescriptionHtml } from '../editor/sceneDescriptionHtml';
+import proseStyles from '../editor/SceneDescriptionModal.module.css';
+import { getDndApi } from '../shared/dndApi';
+
+import styles from './SceneDescriptionApp.module.css';
+
+export function SceneDescriptionApp() {
+  const { t } = useEditorI18n();
+  const [html, setHtml] = useState('');
+
+  useEffect(() => {
+    const api = getDndApi();
+    void api.invoke(ipcChannels.windows.getSceneDescriptionContent, {}).then(({ html: next }) => {
+      setHtml(next);
+    });
+    return api.on(ipcChannels.windows.sceneDescriptionContent, ({ html: next }) => {
+      setHtml(next);
+    });
+  }, []);
+
+  useEffect(() => {
+    const onKey = (e: KeyboardEvent) => {
+      if (e.key === 'Escape') window.close();
+    };
+    window.addEventListener('keydown', onKey);
+    return () => window.removeEventListener('keydown', onKey);
+  }, []);
+
+  const safeHtml = useMemo(() => sanitizeSceneDescriptionHtml(html), [html]);
+  const empty = isSceneDescriptionEmpty(html);
+
+  return (
+    <div className={styles.page}>
+      <div className={styles.body}>
+        {empty ? (
+          <div className={styles.empty}>{t('scene.descriptionEmpty')}</div>
+        ) : (
+          <div
+            className={[proseStyles.prose, styles.proseText].join(' ')}
+            dangerouslySetInnerHTML={{ __html: safeHtml }}
+          />
+        )}
+      </div>
+    </div>
+  );
+}