Add mobile navigation (burger + sidebar drawer)

app/docs.css

@@ -20,10 +20,21 @@
   .docs-shell { grid-template-columns: 240px minmax(0, 1fr) !important; }
   .docs-shell > .docs-toc { display: none !important; }
 }
-@media (max-width: 720px) {
+/* ≤880px the sidebar becomes a slide-in drawer (body.docnav-open contract,
+   opened from the SiteNav burger) — same pattern as the API reference. */
+@media (max-width: 880px) {
   .docs-shell { grid-template-columns: 1fr !important; }
-  .docs-shell > .docs-side { display: none !important; }
-}
+  /* aside.docs-side out-specifies the base `.docs-shell .docs-side` sticky
+     rule below (the grid rules above use !important for the same reason). */
+  .docs-shell > aside.docs-side {
+    position: fixed; top: 0; left: 0; bottom: 0; width: 296px; z-index: 60;
+    height: 100vh; background: var(--bg); border-right: 1px solid var(--line);
+    transform: translateX(-100%); transition: transform .25s; padding-top: 70px;
+  }
+  body.docnav-open .docs-shell > aside.docs-side { transform: none; }
+  body.docnav-open .docs-shell .docnav-scrim { display: block; position: fixed; inset: 0; z-index: 55; background: rgba(0,0,0,.5); }
+}
+.docs-shell .docnav-scrim { display: none; }
 
 .docs-shell {
   /* Design var aliases → framework tokens. Local to the docs shell so they

app/markline-tokens.css

@@ -213,7 +213,39 @@ body {
 /* nav wrap (constrains content width, matches the design) */
 .nav .wrap { width: 100%; max-width: 1240px; margin-inline: auto; padding-inline: 32px; }
 
+/* mobile menu button — hidden on desktop, replaces the nav links ≤880px */
+.nav-burger { display: none; width: 36px; height: 36px; place-items: center; border-radius: 999px; border: 1px solid var(--line); background: transparent; color: var(--ink-2); transition: border-color .15s, color .15s; }
+.nav-burger:hover { color: var(--ink); border-color: var(--ink-4); }
+.nav-burger svg { width: 18px; height: 18px; }
+
+/* fallback dropdown for pages without a sidebar drawer (home, 404) */
+.nav-mobile-panel { display: none; }
+
 @media (max-width: 880px) {
   .nav .wrap { padding-inline: 20px; }
   .nav-links, .ghbadge .lbl { display: none; }
+  .nav-burger { display: grid; flex: none; }
+  /* Fit brand + actions on narrow screens: tighter gaps/padding, smaller logo,
+     and a shrinkable brand so nothing (the burger) gets pushed off-viewport. */
+  .nav-in { gap: 14px; }
+  .nav-in--full, .nav-in--contained { padding-inline: 16px; }
+  .nav-in .brand { min-width: 0; overflow: hidden; }
+  .brand .brand-logo { height: 22px; max-width: 100%; object-position: left center; }
+  .nav-right { gap: 8px; flex: none; }
+  .nav-right .theme-btn, .nav-right .ghbadge { flex: none; }
+  .nav-mobile-panel { display: flex; flex-direction: column; gap: 2px; padding: 10px 14px 14px; border-top: 1px solid var(--line); background: var(--bg); }
+  .nav-mobile-panel a { font-size: 15px; color: var(--ink-2); padding: 11px 10px; border-radius: 9px; text-decoration: none; }
+  .nav-mobile-panel a:hover { color: var(--ink); background: var(--panel-hi); }
+  .nav-mobile-panel a.active { color: var(--ink); font-weight: 500; }
+  .nav-mobile-panel .btn { justify-content: center; margin-top: 8px; }
+}
+
+/* tab links pinned at the top of the mobile sidebar drawer (docs shell) so the
+   top-level sections stay reachable on mobile */
+.drawer-tabs { display: none; }
+@media (max-width: 880px) {
+  .drawer-tabs { display: flex; flex-direction: column; gap: 2px; margin: 0 0 14px; padding-bottom: 12px; border-bottom: 1px solid var(--line); }
+  .drawer-tabs a { display: block; font-size: 13.5px; font-weight: 500; color: var(--ink-2); padding: 8px 10px; border-radius: 8px; text-decoration: none; }
+  .drawer-tabs a:hover { color: var(--ink); background: var(--panel-hi); }
+  .drawer-tabs a.active { color: var(--accent-ink, rgb(var(--c-brand))); background: var(--accent-dim, rgb(var(--c-brand) / 0.10)); }
 }

components/docs/nav.tsx

@@ -143,14 +143,32 @@ export function DocsSidebar({
     return () => cancelAnimationFrame(id);
   }, [pathname]);
 
+  const closeDrawer = () => document.body.classList.remove("docnav-open");
+
   return (
     <>
+      {/* Mobile drawer scrim (body.docnav-open contract — see app/docs.css). */}
+      <div className="docnav-scrim" onClick={closeDrawer} />
       <aside className="docs-side" ref={sideRef}>
+        {tabs.length > 1 && (
+          <nav className="drawer-tabs">
+            {tabs.map((t) => (
+              <Link
+                key={t.id}
+                href={t.href}
+                className={t.id === activeId ? "active" : undefined}
+                onClick={closeDrawer}
+              >
+                {t.label}
+              </Link>
+            ))}
+          </nav>
+        )}
         <div className="docs-tools">
           <SidebarSearchTrigger />
           {ai && <SidebarAskButton />}
         </div>
-        <SidebarSections sections={sections} pathname={pathname} />
+        <SidebarSections sections={sections} pathname={pathname} onNavigate={closeDrawer} />
       </aside>
       {/* Page-level AI affordances (the doc-ai row + View-as-Markdown modal) live
           in the docs shell so they're available on every docs page. */}

components/site-nav.tsx

@@ -52,6 +52,26 @@ export function SiteNav({
   const pathname = usePathname();
   // The homepage ("/") uses its own width knob; every other route uses `width`.
   const layout = pathname === "/" ? homeWidth : width;
+  const [menuOpen, setMenuOpen] = useState(false);
+
+  // Close the mobile menu / page drawer whenever the route changes.
+  useEffect(() => {
+    setMenuOpen(false);
+    document.body.classList.remove("docnav-open");
+  }, [pathname]);
+
+  // Mobile menu button. Pages that ship a sidebar drawer (docs shell, API
+  // reference) use the shared body.docnav-open contract; pages without one
+  // (home, 404) fall back to the SiteNav's own dropdown panel with the links.
+  const onBurger = () => {
+    if (document.querySelector(".docs-side, .api-side")) {
+      setMenuOpen(false);
+      document.body.classList.toggle("docnav-open");
+      return;
+    }
+    document.body.classList.remove("docnav-open");
+    setMenuOpen((v) => !v);
+  };
 
   const isActive = (href: string) => {
     const path = href.split(/[#?]/)[0] || "/";
@@ -105,8 +125,44 @@ export function SiteNav({
               {cta.label}
             </Link>
           )}
+          <button
+            className="nav-burger"
+            type="button"
+            onClick={onBurger}
+            aria-label={menuOpen ? "Close menu" : "Open menu"}
+            aria-expanded={menuOpen}
+          >
+            {menuOpen ? (
+              <svg viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="1.8" aria-hidden="true">
+                <path d="M6 6l12 12M18 6L6 18" />
+              </svg>
+            ) : (
+              <svg viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="1.8" aria-hidden="true">
+                <path d="M4 7h16M4 12h16M4 17h16" />
+              </svg>
+            )}
+          </button>
         </div>
       </div>
+      {menuOpen && (
+        <div className="nav-mobile-panel">
+          {links.map((l) => (
+            <Link
+              key={l.href + l.label}
+              href={l.href}
+              className={isActive(l.href) ? "active" : undefined}
+              onClick={() => setMenuOpen(false)}
+            >
+              {l.label}
+            </Link>
+          ))}
+          {cta && (
+            <Link className="btn btn-primary btn-sm" href={cta.href} onClick={() => setMenuOpen(false)}>
+              {cta.label}
+            </Link>
+          )}
+        </div>
+      )}
     </header>
   );
 }