[BUG] Undo/Redo Stack shared between multiple editor instances

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

Describe the bug
If two or more instances of the editor are used and content has been created in them, when undo/redo is called in one editor, undo/redo is also performed in the other editors when all changes have been completed in the current editor.

Reproduction
https://codesandbox.io/p/sandbox/mdx-editor-base-forked-r7vynx

To Reproduce
Steps to reproduce the behavior:

1. Create two or more editor instances
2. Create content in each of them
3. Undo/redo all changes in one of them and keep doing undo/redo (either with shortcut or with the button in the toolbar)
4. See undo/redo applied to the other editor as well

Expected behavior
Undo/redo only applies to the content of the editor, where it was called.

Video

https://github.com/user-attachments/assets/c775203b-466c-4d3f-a760-63a4e5b09adf

Desktop

• OS: Windows
• Browser: Chrome
• Stack: Next.js App-Router

Additional context
I went back to version 2.0 and the error still occurred. Only when I switched to version 1.* did undo/redo only apply to the content of the editor to which it belongs.

Start by reproducing the issue with the linked CodeSandbox using two editor instances, then trace the undo/redo handling used by the editor and toolbar. Done means undo and redo in one instance never alter another instance, including when keyboard shortcuts are used, with a regression test covering multiple editors.