Markdown 链接中的锚点被 VitePress 修改了

[Tenormis]

Describe the bug

Markdown 链接中以数字开头的锚点（我不确定是否还有其他情况也会有这个问题），编译后会被自动添加 _ 前缀。
In Markdown links, anchors (fragment identifiers) that start with a number (not sure if other cases are also affected) will automatically have an underscore _ prefixed after compilation.

Reproduction

markdown-examples.md:

## 1. Syntax Highlighting

### 1.1. HI 测试标题

[测试链接1](#11-hi-测试标题)

[测试链接2](api-examples.md#2-more)

[测试链接3](api-examples.md#final)

[测试链接4](api-examples.md#最后)

<a href="./api-examples#2-more">HTML 格式链接</a>

api-examples.md:

## 2. More

Check out the documentation for the [full list of runtime APIs](https://vitepress.dev/reference/runtime-api#usedata).

## Final

## 最后

编译后的 markdown-examples.html：
Generated markdown-examples.html:

<p><a href="#_11-hi-测试标题">测试链接1</a></p>
<p><a href="./api-examples#_2-more">测试链接2</a></p>
<p><a href="./api-examples#final">测试链接3</a></p>
<p><a href="./api-examples#最后">测试链接4</a></p>
<p><a href="./api-examples#2-more">HTML 格式链接</a></p>

“测试链接1” 和 “测试链接2” 的原始锚点被篡改了（添加了 _ 前缀）。
The original anchors for “Test Link 1” and “Test Link 2” were altered (an underscore _ was added).

“测试链接3”、“测试链接4”、“HTML 格式链接” 没有问题（保持原值不变）。
“Test Link 3”, “Test Link 4”, and the HTML-formatted link are unaffected (the original values remain unchanged).

Expected behavior

“测试链接1” 和 “测试链接2” 的锚点不应被篡改。
The anchors for “Test Link 1” and “Test Link 2” should not be modified.

System Info

略 (omitted)

Additional context

No response

Validations

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• Follow our Code of Conduct
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.

[brc-dd]

An HTML id cannot start with a number.

[Tenormis]

An HTML id cannot start with a number.

Oh, you're right. I ignored the HTML id format requirement