feat: render current spec on index page instead of redirecting

- Update index.astro to fetch and render the current spec version
  directly rather than redirecting to /spec/{version}
- Move .spec-content styles from [version].astro to global.css
  to share styles between index and version pages
- Rebuild site with new index page

src/styles/global.css

@@ -132,4 +132,80 @@
   .menu-link {
     transition: all 0.2s ease-out;
   }
+
+  /* Spec content styling */
+  .spec-content h1 {
+    margin-bottom: 0.5em;
+  }
+
+  .spec-content h2 {
+    margin-top: 2em;
+    margin-bottom: 0.75em;
+    padding-bottom: 0.3em;
+    border-bottom: 1px solid #eee;
+  }
+
+  .dark .spec-content h2 {
+    border-bottom-color: #333;
+  }
+
+  .spec-content h3 {
+    margin-top: 1.5em;
+    margin-bottom: 0.5em;
+  }
+
+  .spec-content p {
+    margin-bottom: 1em;
+  }
+
+  .spec-content ul,
+  .spec-content ol {
+    margin-bottom: 1em;
+    padding-left: 2em;
+  }
+
+  .spec-content li {
+    margin-bottom: 0.25em;
+  }
+
+  .spec-content a {
+    color: #1f8dd6;
+    text-decoration: none;
+  }
+
+  .spec-content a:hover {
+    text-decoration: underline;
+  }
+
+  .dark .spec-content a {
+    color: #4da6e8;
+  }
+
+  .spec-content img {
+    max-width: 100%;
+    height: auto;
+    margin: 1em 0;
+  }
+
+  .spec-content blockquote {
+    margin: 1em 0;
+    padding-left: 1em;
+    border-left: 4px solid #ddd;
+    color: #666;
+  }
+
+  .dark .spec-content blockquote {
+    border-left-color: #444;
+    color: #aaa;
+  }
+
+  .spec-content hr {
+    margin: 2em 0;
+    border: none;
+    border-top: 1px solid #eee;
+  }
+
+  .dark .spec-content hr {
+    border-top-color: #333;
+  }
 }