Publish automation discovery descriptor immediately

src/app/control/transport.rs

@@ -52,6 +52,7 @@ fn listen(sender: mpsc::Sender<Envelope>) -> std::io::Result<()> {
     }
     let mut file = options.open(&path)?;
     write!(file, "{descriptor}")?;
+    drop(file);
     let clients = Arc::new(AtomicUsize::new(0));
     for stream in listener.incoming().flatten() {
         if clients.fetch_add(1, Ordering::SeqCst) >= 8 {