[BUG] allowedHeadingLevels not working with markdown shortcuts

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• [o] I have searched for similar issues in both open and closed tickets and cannot find a duplicate.
• [o] I have read the documentation and cannot find an answer.

Describe the bug

After setting allowedHeadingLevels [1,2], but ### + spacebar shortcut makes h3 tag. also h4, h5, h6.

export default function InitializedMDXEditor({
  editorRef,
  ...props
}: { editorRef: ForwardedRef<MDXEditorMethods> | null } & MDXEditorProps) {
  return (
    <MDXEditor
      plugins={[
        headingsPlugin({
          allowedHeadingLevels: [1, 2],
        }),
        markdownShortcutPlugin(),
      ]}
      {...props}
      ref={editorRef}
    />
  );
}

Reproduction
Start from https://codesandbox.io/p/sandbox/mdx-editor-base-q8s7zr?file=/src/App.tsx to reproduce the problem so that I can observe the issue on my side and make sure that the fix reliably addresses it.

To Reproduce
Steps to reproduce the behavior:

1. Go to '...'
2. Click on '....'
3. Scroll down to '....'
4. See error

Expected behavior

I set allowedHeadingLevels = [1,2] but ### or #### or ##### or ###### still working.

Screenshots
If applicable, add screenshots to help explain your problem.

https://github.com/user-attachments/assets/7e5f5c99-789f-4bc4-a682-fe760de621c5

Desktop (please complete the following information):

• MacOs, tauri

Start with the linked CodeSandbox reproduction in src/App.tsx, using headingsPlugin with allowedHeadingLevels [1,2] and markdownShortcutPlugin. Trace how the markdown heading shortcuts are handled and verify that ### through ###### no longer create headings outside the allowed levels.