Fix Agent node structured output not updating flow state variables (#5548)

Fix Agent state processing for structured output

Updated the Agent class to handle structured output by passing a JSON string instead of a markdown-wrapped response to the `processTemplateVariables` function. This change allows for proper nested property access and resolves string replacement issues with object coercion.

packages/components/nodes/agentflow/Agent/Agent.ts

@@ -1394,7 +1394,9 @@ class Agent_Agentflow implements INode {
             }
 
             // Process template variables in state
-            newState = processTemplateVariables(newState, finalResponse)
+            const outputForStateProcessing =
+                isStructuredOutput && typeof response === 'object' ? JSON.stringify(response, null, 2) : finalResponse
+            newState = processTemplateVariables(newState, outputForStateProcessing)
 
             /**
              * Remove the temporarily added image artifact messages before storing