feat: add collapsible mobile ToC for in-page navigation

.gitignore

@@ -26,6 +26,9 @@ dist/
 # JetBrains IDE
 .idea/
 
+# Claude Code
+.claude/
+
 # Unit test reports
 TEST*.xml
 

astro-site/src/components/Header.astro

@@ -90,4 +90,5 @@ const base = import.meta.env.BASE_URL;
     navToggle.setAttribute("aria-expanded", "false");
     siteTabs.classList.remove("open");
   });
+
 </script>

astro-site/src/components/MobileToc.astro

@@ -0,0 +1,60 @@
+---
+interface Heading {
+  depth: number;
+  slug: string;
+  text: string;
+}
+
+const { headings = [] } = Astro.props as { headings: Heading[] };
+const h2s = headings.filter((h) => h.depth === 2);
+---
+
+{h2s.length > 0 && (
+  <div class="mobile-toc" id="mobile-toc">
+    <button class="mobile-toc-fab" id="mobile-toc-fab" aria-label="Table of contents" aria-expanded="false">
+      <svg viewBox="0 0 24 24" width="24" height="24" fill="currentColor" aria-hidden="true">
+        <path d="M3 18h18v-2H3v2zm0-5h18v-2H3v2zm0-7v2h18V6H3z"/>
+      </svg>
+    </button>
+    <div class="mobile-toc-overlay" id="mobile-toc-overlay">
+      <div class="mobile-toc-header">On this page</div>
+      <ul>
+        {h2s.map((h) => (
+          <li>
+            <a href={`#${h.slug}`}>{h.text}</a>
+          </li>
+        ))}
+      </ul>
+    </div>
+  </div>
+)}
+
+<script is:inline>
+  (function () {
+    var fab = document.getElementById("mobile-toc-fab");
+    var overlay = document.getElementById("mobile-toc-overlay");
+    var toc = document.getElementById("mobile-toc");
+    if (!fab || !overlay) return;
+
+    fab.addEventListener("click", function (e) {
+      e.stopPropagation();
+      var open = fab.getAttribute("aria-expanded") === "true";
+      fab.setAttribute("aria-expanded", String(!open));
+      overlay.classList.toggle("open");
+    });
+
+    overlay.querySelectorAll("a").forEach(function (link) {
+      link.addEventListener("click", function () {
+        fab.setAttribute("aria-expanded", "false");
+        overlay.classList.remove("open");
+      });
+    });
+
+    document.addEventListener("click", function (e) {
+      if (!overlay.classList.contains("open")) return;
+      if (toc.contains(e.target)) return;
+      fab.setAttribute("aria-expanded", "false");
+      overlay.classList.remove("open");
+    });
+  })();
+</script>

astro-site/src/layouts/DocLayout.astro

@@ -4,6 +4,7 @@ import Header from "../components/Header.astro";
 import TableOfContents from "../components/TableOfContents.astro";
 import TutorialLinks from "../components/TutorialLinks.astro";
 import Footer from "../components/Footer.astro";
+import MobileToc from "../components/MobileToc.astro";
 import site from "../data/site.json";
 
 interface Props {
@@ -71,6 +72,7 @@ const ogImage = new URL("/tutorial-git/images/og-banner.png", Astro.site);
       <div class="resize-handle" data-side="right"></div>
       <TutorialLinks />
     </div>
+    <MobileToc headings={headings} />
     <Footer />
 
     <script is:inline>

astro-site/src/styles/global.css

@@ -572,8 +572,83 @@ a:hover {
   color: var(--color-fg-muted);
 }
 
+/* Mobile ToC — floating button, hidden on desktop */
+.mobile-toc {
+  display: none;
+}
+
 /* Responsive */
 @media (max-width: 960px) {
+  .mobile-toc {
+    display: block;
+    position: fixed;
+    bottom: var(--space-lg);
+    right: var(--space-lg);
+    z-index: 100;
+  }
+
+  .mobile-toc-fab {
+    width: 48px;
+    height: 48px;
+    border-radius: 50%;
+    border: none;
+    background: var(--color-primary);
+    color: #fff;
+    cursor: pointer;
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.25);
+  }
+
+  .mobile-toc-fab:hover {
+    background: var(--color-primary-dark);
+  }
+
+  .mobile-toc-overlay {
+    display: none;
+    position: absolute;
+    bottom: 56px;
+    right: 0;
+    width: 250px;
+    max-height: 60vh;
+    overflow-y: auto;
+    background: var(--color-bg);
+    border: 1px solid var(--color-border);
+    border-radius: 8px;
+    box-shadow: 0 4px 16px rgba(0, 0, 0, 0.15);
+    padding: var(--space-sm) 0;
+  }
+
+  .mobile-toc-overlay.open {
+    display: block;
+  }
+
+  .mobile-toc-header {
+    padding: var(--space-sm) var(--space-md);
+    font-size: var(--font-size-sm);
+    font-weight: 600;
+    color: var(--color-fg-muted);
+  }
+
+  .mobile-toc-overlay ul {
+    list-style: none;
+    padding: 0;
+  }
+
+  .mobile-toc-overlay li a {
+    display: block;
+    padding: var(--space-xs) var(--space-md);
+    color: var(--color-fg);
+    text-decoration: none;
+    font-size: var(--font-size-sm);
+  }
+
+  .mobile-toc-overlay li a:hover {
+    background: var(--color-bg-hover);
+    color: var(--color-link);
+  }
+
   .site-main {
     grid-template-columns: 1fr;
   }