test(core): use editor.unmount() instead of _tiptapEditor.destroy()

unmount() is the public API for tearing down a BlockNoteEditor and handles
portalElement cleanup in addition to the underlying prosemirror teardown.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: nperez0111

packages/core/src/blocks/ListItem/NumberedListItem/IndexingPlugin.test.ts

@@ -9,15 +9,15 @@ import { BlockNoteEditor } from "../../../editor/BlockNoteEditor.js";
 
 const PLUGIN_KEY = "numbered-list-indexing-decorations$";
 
-// Track editors created in each test so we can destroy them in afterEach —
+// Track editors created in each test so we can unmount them in afterEach —
 // otherwise prosemirror-view's DOMObserver leaves a setTimeout alive that
 // fires after vitest tears down jsdom, throwing
 // `ReferenceError: document is not defined` and failing the run.
 const activeEditors: BlockNoteEditor<any, any, any>[] = [];
 
 afterEach(() => {
   while (activeEditors.length) {
-    activeEditors.pop()!._tiptapEditor.destroy();
+    activeEditors.pop()!.unmount();
   }
 });