Feat: If a query variable in a data manipulation operator is deleted, a warning message should be displayed to the user. #10427 #11255 (#11384)

### What problem does this PR solve?

Feat: If a query variable in a data manipulation operator is deleted, a
warning message should be displayed to the user. #10427 #11255

### Type of change


- [x] New Feature (non-breaking change which adds functionality)

web/src/pages/agent/form/components/dynamic-fom-header.tsx

@@ -7,17 +7,24 @@ export type FormListHeaderProps = {
   label: ReactNode;
   tooltip?: string;
   onClick?: () => void;
+  disabled?: boolean;
 };
 
 export function DynamicFormHeader({
   label,
   tooltip,
   onClick,
+  disabled = false,
 }: FormListHeaderProps) {
   return (
     <div className="flex items-center justify-between">
       <FormLabel tooltip={tooltip}>{label}</FormLabel>
-      <Button variant={'ghost'} type="button" onClick={onClick}>
+      <Button
+        variant={'ghost'}
+        type="button"
+        onClick={onClick}
+        disabled={disabled}
+      >
         <Plus />
       </Button>
     </div>