feat: add sticky sidebar navigation to learning hub articles

website/public/styles/global.css

@@ -1594,6 +1594,84 @@ a:hover {
   color: var(--color-warning);
 }
 
+/* Learning Hub - Sidebar Layout */
+.learning-hub-layout {
+  display: grid;
+  grid-template-columns: 240px 1fr;
+  gap: 48px;
+  align-items: start;
+}
+
+.learning-hub-sidebar {
+  position: sticky;
+  top: 24px;
+  max-height: calc(100vh - 48px);
+  overflow-y: auto;
+}
+
+.sidebar-section {
+  margin-bottom: 24px;
+}
+
+.sidebar-section h3 {
+  font-size: 11px;
+  font-weight: 700;
+  text-transform: uppercase;
+  letter-spacing: 0.08em;
+  color: var(--color-text-muted);
+  margin-bottom: 8px;
+  padding: 0 12px;
+}
+
+.sidebar-nav-list {
+  list-style: none;
+  padding: 0;
+  margin: 0;
+}
+
+.sidebar-nav-list li {
+  margin: 0;
+}
+
+.sidebar-nav-list a {
+  display: block;
+  padding: 6px 12px;
+  font-size: 13px;
+  line-height: 1.4;
+  color: var(--color-text-muted);
+  text-decoration: none;
+  border-radius: 6px;
+  border-left: 2px solid transparent;
+  transition: color 0.15s, background-color 0.15s, border-color 0.15s;
+}
+
+.sidebar-nav-list a:hover {
+  color: var(--color-text);
+  background-color: var(--color-glass);
+}
+
+.sidebar-nav-list a.active {
+  color: var(--color-text-emphasis);
+  background-color: var(--color-glass);
+  border-left-color: var(--color-accent);
+  font-weight: 600;
+}
+
+@media (max-width: 900px) {
+  .learning-hub-layout {
+    grid-template-columns: 1fr;
+    gap: 0;
+  }
+
+  .learning-hub-sidebar {
+    position: static;
+    max-height: none;
+    border-bottom: 1px solid var(--color-border);
+    padding-bottom: 20px;
+    margin-bottom: 32px;
+  }
+}
+
 /* Learning Hub - Article Styles */
 .breadcrumb {
   margin-bottom: 16px;

website/src/layouts/ArticleLayout.astro

@@ -1,5 +1,6 @@
 ---
 import BaseLayout from './BaseLayout.astro';
+import { getCollection } from 'astro:content';
 
 interface Props {
   title: string;
@@ -11,6 +12,31 @@ interface Props {
 
 const { title, description, estimatedReadingTime, lastUpdated, tags } = Astro.props;
 const base = import.meta.env.BASE_URL;
+
+const articles = await getCollection('learning-hub');
+
+const fundamentalsOrder = [
+  'what-are-agents-prompts-instructions',
+  'understanding-copilot-context',
+  'copilot-configuration-basics',
+  'defining-custom-instructions',
+  'creating-effective-prompts',
+  'before-after-customization-examples',
+];
+
+const referenceOrder = [
+  'github-copilot-terminology-glossary',
+];
+
+const fundamentals = articles
+  .filter((a) => fundamentalsOrder.includes(a.id))
+  .sort((a, b) => fundamentalsOrder.indexOf(a.id) - fundamentalsOrder.indexOf(b.id));
+
+const reference = articles
+  .filter((a) => referenceOrder.includes(a.id))
+  .sort((a, b) => referenceOrder.indexOf(a.id) - referenceOrder.indexOf(b.id));
+
+const currentSlug = Astro.url.pathname.replace(/\/$/, '').split('/').pop();
 ---
 
 <BaseLayout title={title} description={description} activeNav="learning-hub">
@@ -38,9 +64,45 @@ const base = import.meta.env.BASE_URL;
 
     <div class="page-content">
       <div class="container">
-        <article class="article-content">
-          <slot />
-        </article>
+        <div class="learning-hub-layout">
+          <nav class="learning-hub-sidebar" aria-label="Learning Hub articles">
+            <div class="sidebar-section">
+              <h3>Fundamentals</h3>
+              <ol class="sidebar-nav-list">
+                {fundamentals.map((article) => (
+                  <li>
+                    <a
+                      href={`${base}learning-hub/${article.id}/`}
+                      class={currentSlug === article.id ? 'active' : ''}
+                      aria-current={currentSlug === article.id ? 'page' : undefined}
+                    >
+                      {article.data.title}
+                    </a>
+                  </li>
+                ))}
+              </ol>
+            </div>
+            <div class="sidebar-section">
+              <h3>Reference</h3>
+              <ul class="sidebar-nav-list">
+                {reference.map((article) => (
+                  <li>
+                    <a
+                      href={`${base}learning-hub/${article.id}/`}
+                      class={currentSlug === article.id ? 'active' : ''}
+                      aria-current={currentSlug === article.id ? 'page' : undefined}
+                    >
+                      {article.data.title}
+                    </a>
+                  </li>
+                ))}
+              </ul>
+            </div>
+          </nav>
+          <article class="article-content">
+            <slot />
+          </article>
+        </div>
       </div>
     </div>
   </main>