🐛 [Bug]: 支持markdown语法后，使用##会出现上边框

[CatsAndMice]

Version

4.0.0-alpha.1

Link to minimal reproduction

支持markdown语法后，使用##会出现上边框，而且无法删除

Step to reproduce

官网dome可复现：https://opentiny.github.io/tiny-editor/docs/demo/markdown

What is expected

No response

What is actually happening

No response

What is your project name

官网dome

Any additional comments (optional)

No response

[kagol]

应该是 demo 被 VitePress 的样式影响了