onboard now derives defaults from env vars before writing config

cli/src/prompts/server.ts

@@ -149,7 +149,14 @@ export async function promptServer(opts?: {
   }
 
   return {
-    server: { deploymentMode, exposure, host: hostStr.trim(), port, allowedHostnames, serveUi: true },
+    server: {
+      deploymentMode,
+      exposure,
+      host: hostStr.trim(),
+      port,
+      allowedHostnames,
+      serveUi: currentServer?.serveUi ?? true,
+    },
     auth,
   };
 }