Feat: Add child nodes and their connecting lines by clicking #3221 (#8314)

### What problem does this PR solve?
Feat: Add child nodes and their connecting lines by clicking #3221

### Type of change


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

web/src/pages/agent/constant.tsx

@@ -3008,3 +3008,8 @@ export const NoDebugOperatorsList = [
   Operator.Switch,
   Operator.Iteration,
 ];
+
+export enum NodeHandleId {
+  Start = 'start',
+  End = 'end',
+}