fix(editor): avoid accessing editor.view during initial render in link preview

EditorLinkPreview's useRef initializer accessed editor.view?.dom which
throws when the editor view is not yet mounted (Tiptap uses a Proxy
that rejects property access before mount). Defer the contextElement
assignment to the selectionUpdate callback where the view is guaranteed
to exist.

packages/views/editor/link-preview.tsx

@@ -156,9 +156,10 @@ function EditorLinkPreview({ editor }: { editor: Editor }) {
 
   const close = useCallback(() => setVisible(false), []);
 
+  // Avoid accessing editor.view during initial render — it may not be mounted yet.
   const virtualRef = useRef({
     getBoundingClientRect: () => new DOMRect(),
-    contextElement: editor.view?.dom,
+    contextElement: undefined as Element | undefined,
   });
 
   const { refs, floatingStyles, isPositioned, update } = useFloating({