fix(dashboard): remove unused onBack prop from Sidebar

packages/dashboard/src/app.tsx

@@ -13,7 +13,7 @@ export function App() {
 
   return (
     <div className="flex h-screen">
-      <Sidebar view={view} onViewChange={setView} onBack={() => setSelectedThread(null)} />
+      <Sidebar view={view} onViewChange={setView} />
       <main className="flex-1 overflow-hidden flex flex-col">
         <StatusBar />
         <div className="flex-1 overflow-auto p-6">

packages/dashboard/src/components/sidebar.tsx

@@ -1,7 +1,6 @@
 type Props = {
   view: "threads" | "workflows";
   onViewChange: (v: "threads" | "workflows") => void;
-  onBack: () => void;
 };
 
 export function Sidebar({ view, onViewChange }: Props) {