feat: chat reactions

components/layout/site-mobile-nav.tsx

@@ -17,6 +17,7 @@ import { useState } from "react";
 import Link from "next/link";
 import { Menu } from "lucide-react";
 import { cn } from "@/lib/utils";
+import { useHidesAppChrome } from "@/lib/use-chrome-visibility";
 import {
   Drawer,
   DrawerContent,
@@ -43,6 +44,10 @@ export function MobileNavToggle({
   items: ReadonlyArray<NavItem>;
 }) {
   const [open, setOpen] = useState(false);
+  // A thread already has a back button in its own header; a hamburger beside
+  // it offers a second, conflicting way out.
+  const hidden = useHidesAppChrome();
+  if (hidden) return null;
 
   return (
     <Drawer open={open} onOpenChange={setOpen} direction="left">