Fix code block font size on mobile (too large)

Root cause: mobile Safari inflates text inside `pre` elements when
content is wider than the viewport, overriding the computed font-size.
The existing `text-size-adjust: 100%` on `html` does not propagate
fully to `pre` elements with `overflow: auto`.

Fix:
- Add `-webkit-text-size-adjust: 100%` directly on pre/code/prism-code
  to prevent mobile Safari text inflation
- Add mobile media query (max-width: 768px) reducing code block font
  to 12px for better visual proportion on small screens

https://claude.ai/code/session_01UjvipgoS6qs1ikzifd77Xi

Author: claude

src/css/custom.css

@@ -24,10 +24,19 @@
   --ifm-pre-line-height: 1.3;
 }
 
-/* Code blocks: 14px font, normal line height */
+/* Code blocks: consistent font, prevent mobile Safari text inflation */
 pre, pre code, .prism-code {
   font-size: 14px !important;
   line-height: 1.5 !important;
+  -webkit-text-size-adjust: 100%;
+  text-size-adjust: 100%;
+}
+
+/* Smaller code blocks on mobile for better readability */
+@media (max-width: 768px) {
+  pre, pre code, .prism-code {
+    font-size: 12px !important;
+  }
 }
 
 /* ASCII diagrams: no line gaps for proper character alignment */