Improve chat navigation, model selection, and streaming

app/layout.tsx

@@ -3,9 +3,28 @@ import type { Metadata } from 'next';
 import { ThemeProvider } from '@/components/theme-provider';
 import './globals.css';
 
+const title = 'ChatGPT Agent | AI Chat & Research Assistant';
+const description =
+  'Ask questions, explore ideas, and get clear AI answers with streaming responses, optional web research, file attachments, and saved conversations.';
+
 export const metadata: Metadata = {
-  title: 'ChatGPT Agent',
-  description: 'A ChatGPT-powered assistant for clear, useful answers.',
+  applicationName: 'ChatGPT Agent',
+  title: {
+    default: title,
+    template: '%s | ChatGPT Agent',
+  },
+  description,
+  openGraph: {
+    type: 'website',
+    siteName: 'ChatGPT Agent',
+    title,
+    description,
+  },
+  twitter: {
+    card: 'summary',
+    title,
+    description,
+  },
 };
 
 export default function RootLayout({