fix: hide suggestions when chat has messages

- Change suggestion availability from 'always' to 'on-empty'
- Prompts now only show in empty chat
- Hides clutter when conversation is ongoing

Author: jerelvelarde

apps/app/src/app/canvas/page.tsx

@@ -222,7 +222,7 @@ const DocumentEditor = () => {
         message: "Write a detailed document about continuous integration and continuous deployment, covering stages, automated testing, build artifacts, and deployment strategies.",
       },
     ],
-    available: "always",
+    available: "on-empty",
   });
 
   const { agent } = useAgent({