mobile save config when disable input

flutter/lib/models/server_model.dart

@@ -263,8 +263,11 @@ class ServerModel with ChangeNotifier {
   toggleInput() {
     if (_inputOk) {
       parent.target?.invokeMethod("stop_input");
+      bind.mainSetOption(key: "enable-keyboard", value: 'N');
     } else {
       if (parent.target != null) {
+        /// the result of toggle-on depends on user actions in the settings page.
+        /// handle result, see [ServerModel.changeStatue]
         showInputWarnAlert(parent.target!);
       }
     }