Fix builder not saving correctly and workflow agent saves model field

Author: wyf7107

src/app/core/models/AgentBuilder.ts

@@ -48,7 +48,7 @@ export interface CallbackNode {
 
 export interface YamlConfig {
   name: string;
-  model: string;
+  model?: string;
   agent_class: string;
   description?: string;
   instruction?: string;

src/app/core/services/agent-builder.service.ts

@@ -118,9 +118,7 @@ export class AgentBuilderService implements AgentBuilderServiceInterface {
   }
 
   setSelectedNode(node: AgentNode | undefined) {
-    // Create a shallow copy to ensure change detection triggers
-    const nodeCopy = node ? { ...node } : undefined;
-    this.selectedNodeSubject.next(nodeCopy);
+    this.selectedNodeSubject.next(node);
   }
 
   getSelectedTool(): Observable<ToolNode|undefined> {

src/utils/yaml-utils.ts

@@ -52,6 +52,7 @@ export class YamlUtils {
     }
 
     if (agentNode.agent_class != "LlmAgent") {
+      delete yamlConfig.model;
       delete yamlConfig.instruction;
       delete yamlConfig.tools;
     }