Markdown-to-HTML conversion escapes matrix separators (&) to &, which causes KaTeX to render amp; text and break matrix alignment in preview. This PR updates the math rendering path so LaTeX receives the expected separators.

• Math rendering fix (preview.js)

  • In renderKaTeX(), decode & back to & for extracted TeX content before calling katex.renderToString(...).
  • Scope is intentionally narrow: only matrix-relevant ampersand unescaping in KaTeX input.

• Behavioral impact

  • LaTeX matrices using escaped separators now render with correct column structure.
  • Non-math HTML escaping behavior remains unchanged.

function decodeHtmlEntities(text) {
  return text.replace(/&/g, '&');
}

html = html.replace(/\$\$([\s\S]+?)\$\$/g, function(m, tex) {
  return katex.renderToString(decodeHtmlEntities(tex).trim(), { displayMode: true, throwOnError: false });
});

• Issue context screenshot
  • https://github.com/user-attachments/assets/e4e6d4ef-ef1a-4209-8898-8688e493fe88