fix: escape footnote tooltip content in aria-label

[xwbcl123]

Summary

• escape footnote tooltip text before inserting it into aria-label
• prevent footnote hover markup from breaking when the footnote content contains quotes

Problem

The footnote tooltip renderer currently does stripHTML() and then injects the result directly into:

<span class="hint--top hint--rounded" aria-label="...">

If the footnote content contains quotes, the generated aria-label can break and the hover span markup may be rendered as visible text instead of a tooltip.

Reproduction

A footnote like this is enough to trigger it:

[^4]: ... Jim Nightingale ("Jim the AI Whisperer") ...
[^5]: ... internal Agent "Goose" ...

Fix

Apply HTML attribute escaping to the stripped footnote text before concatenating it into aria-label.

Validation

• reproduced the issue in a local Hexo site using Fluid
• rebuilt the site after the patch
• verified that the generated footnote refs now render as valid tooltip markup
• verified that no leaked <span class=...> text appears in the page body