serve the fonts in woff2 and only preload the ones used on every page

- convert Source Serif Pro and Source Sans Pro to woff2 (lossless,
  ~500 KB -> ~155 KB) and only declare the woff2 format, which is
  supported by all current browsers
- only preload the body and menu fonts: JetBrains Mono is only used by
  code blocks. Previously, five fonts were preloaded (~800 KB), including
  JetBrains Mono in three formats.
- remove the unused material-icons fonts (icons are inline SVG)

Refs #11

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01YNHsWYTXPThURz6TbVS1j3

assets/css/itix.css

@@ -41,9 +41,7 @@
  */
 @font-face{
   font-family: 'JetBrains Mono';
-  src: url('/fonts/JetBrainsMono-Regular.woff2') format('woff2'),
-    url('/fonts/JetBrainsMono-Regular.woff') format('woff'),
-    url('/fonts/JetBrainsMono-Regular.ttf') format('truetype');
+  src: url('/fonts/JetBrainsMono-Regular.woff2') format('woff2');
   font-weight: 400;
   font-style: normal;
 
@@ -57,7 +55,7 @@
 
 @font-face{
   font-family: 'Source Serif Pro';
-  src: url('/fonts/SourceSerifPro-Regular.ttf') format('truetype');
+  src: url('/fonts/SourceSerifPro-Regular.woff2') format('woff2');
   font-weight: 400;
   font-style: normal;
 
@@ -71,7 +69,7 @@
 
 @font-face{
   font-family: 'Source Sans Pro';
-  src: url('/fonts/SourceSansPro-Regular.ttf') format('truetype');
+  src: url('/fonts/SourceSansPro-Regular.woff2') format('woff2');
   font-weight: 400;
   font-style: normal;
 

layouts/_partials/head.html

@@ -14,13 +14,11 @@
 <!--
   -- Core Web Vitals / Cumulative Layout Shift.
   --
-  -- Preload all fonts and images to reduce layout shifts.
+  -- Preload the fonts used on every page (body text, menu and toolbar).
+  -- The monospace font is only used by code blocks: it is not preloaded.
   -->
-<link rel="preload" href="/fonts/JetBrainsMono-Regular.woff2" as="font" type="font/woff2" crossorigin="anonymous">
-<link rel="preload" href="/fonts/JetBrainsMono-Regular.woff" as="font" type="font/woff" crossorigin="anonymous">
-<link rel="preload" href="/fonts/JetBrainsMono-Regular.ttf" as="font" type="font/ttf" crossorigin="anonymous">
-<link rel="preload" href="/fonts/SourceSerifPro-Regular.ttf" as="font" type="font/ttf" crossorigin="anonymous">
-<link rel="preload" href="/fonts/SourceSansPro-Regular.ttf" as="font" type="font/ttf" crossorigin="anonymous">
+<link rel="preload" href="/fonts/SourceSerifPro-Regular.woff2" as="font" type="font/woff2" crossorigin="anonymous">
+<link rel="preload" href="/fonts/SourceSansPro-Regular.woff2" as="font" type="font/woff2" crossorigin="anonymous">
 
 <!--
   -- Add a reference to the favicon.ico.