.NET Workflows - Fix converation behaviors for declarative worfklows (#1237)

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* Update dotnet/tests/Microsoft.Agents.AI.Workflows.Declarative.IntegrationTests/Workflows/ConversationMessages.yaml

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

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Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

workflow-samples/Marketing.yaml

@@ -14,13 +14,6 @@ trigger:
   id: workflow_demo
   actions:
 
-    - kind: AddConversationMessage
-      id: add_input_message
-      conversationId: =System.ConversationId
-      content:
-        - type: Text
-          value: {System.LastMessage.Text}
-
     - kind: InvokeAzureAgent
       id: invoke_analyst
       conversationId: =System.ConversationId

workflow-samples/MathChat.yaml

@@ -31,22 +31,11 @@ trigger:
   id: workflow_demo
   actions:
 
-    - kind: SetVariable
-      id: set_project
-      variable: Local.InputTask
-      value: =UserMessage(System.LastMessageText)
-
     - kind: InvokeAzureAgent
       id: question_student
       conversationId: =System.ConversationId
       agent:
         name: =Env.FOUNDRY_AGENT_STUDENT
-      input:
-        messages: =Local.InputTask
-
-    - kind: ResetVariable
-      id: reset_project
-      variable: Local.InputTask
 
     - kind: InvokeAzureAgent
       id: question_teacher