Converted all external tool calling to async

server/src/main.rs

@@ -492,7 +492,7 @@ async fn main() -> Result<(), std::io::Error> {
     tokio::time::sleep(std::time::Duration::from_millis(1500)).await;
 
     // Kill all active PTY child processes before exiting.
-    agents_for_shutdown.kill_all_children();
+    agents_for_shutdown.kill_all_children().await;
 
     if let Some(ref path) = port_file {
         remove_port_file(path);