[BUG] The frontmatter is included when copying content.

• 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
When I copy content from the top section in rich text mode, the frontmatter content gets copied along with it. When I paste it, the frontmatter is pasted together with the main content into the editor, causing unexpected results.

Reproduction

To Reproduce
Steps to reproduce the behavior:

1. In the live demo, switch to source mode and write the frontmatter
2. Switch to rich mode and move your cursor to the top area
3. Use the shortcut shift + cmd + ⬆️ to select the content in the upper area
4. Copy and paste
5. Switch back to source mode and you'll find that the frontmatter has been copied
   and pasted multiple times along with the main content

Expected behavior
When copying main content in rich mode, it should not include invisible frontmatter information.

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

Desktop (please complete the following information):

• OS: MacOS
• Browser：Chromium 134.0.6998.89

Additional context
Add any other context about the problem here.

Reproduce the issue in the live demo by adding frontmatter in source mode, switching to rich mode, selecting from the top area, and copying and pasting. Verify the rich-mode copy boundary excludes invisible frontmatter and that switching back to source mode shows no duplicated frontmatter.