Fix welcome page columns for four cards

Co-authored-by: Zeyu (Zayne) Zhang <zeyu2001@users.noreply.github.com>

Author: cursoragent

index.mdx

@@ -10,7 +10,7 @@ Meet the next generation of AI-native tools built for developers, security engin
 
 ## Hacktron Workbench
 
-<Columns cols={3}>
+<Columns cols={4}>
   <Card
     title="CLI Quickstart"
     icon="terminal"