refactor(math): use native MathML instead of KaTeX CDN

Remove external KaTeX stylesheet dependency in favor of browser-native
MathML rendering. Aligns with suckless philosophy—zero external deps,
works offline, smaller page loads.

- Remove KaTeX CDN links from base.html
- Hide katex-html layer, let browsers render MathML natively
- Clean up obsolete CSS (.hide-tail, .katex-display)
- Add minimal .math-display for block math layout

docs/static/style.css

@@ -262,22 +262,19 @@ a:hover {
   color: var(--accent-hover);
 }
 
-/* KaTeX display math - local overrides */
+/* Math (native MathML rendering) */
-.katex-display {
+.math-display {
+  display: block;
   margin: 1rem 0;
   overflow-x: auto;
+  text-align: center;
 }
 
-/* Hide katex-html (requires CDN fonts), use native MathML rendering instead */
+/* Hide KaTeX HTML layer, use browser's native MathML instead */
 .katex-html {
   display: none;
 }
 
-/* Fallback: constrain radical SVG when CDN blocked */
-.hide-tail svg {
-  max-width: 100% !important;
-}
-
 /* Code */
 code {
   font-family:

docs/templates/base.html

@@ -9,12 +9,6 @@
   <title>{{ title }} | {{ config.title }}</title>
   <link rel="canonical" href="{{ base_url }}{{ page_path }}" />
   <link rel="stylesheet" href="{{ prefix }}/style.css" />
-  <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/katex@0.16.21/dist/katex.min.css" crossorigin="anonymous"
-    media="print" onload="this.media='all'" />
-  <noscript>
-    <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/katex@0.16.21/dist/katex.min.css"
-      crossorigin="anonymous" />
-  </noscript>
   <link rel="icon" type="image/png" href="{{ prefix }}/logo.png" />
 </head>