AX Agent 최종 응답 커밋 흐름을 엔진으로 통합

- AxAgentExecutionEngine에 FinalizeAssistantTurn을 추가해 assistant 최종 내용 정규화, Cowork/Code 실행 로그 접힘, 메시지 커밋을 한 메서드로 통합함

- SendMessageAsync와 SendRegenerateAsync가 동일한 엔진 마무리 경로를 타도록 정리해 UI 쪽 중복 후처리를 줄임

- 검증: dotnet build src/AxCopilot/AxCopilot.csproj -c Release -v minimal -p:OutputPath=bin\\verify\\ -p:IntermediateOutputPath=obj\\verify\\ 경고 0 / 오류 0

src/AxCopilot/Views/ChatWindow.xaml.cs

@@ -8465,14 +8465,10 @@ public partial class ChatWindow : Window
             SetStatusIdle();
         }
 
-        assistantContent = _chatEngine.NormalizeAssistantContent(conv, runTab, assistantContent);
-        if (runTab is "Cowork" or "Code")
-            conv.ShowExecutionHistory = false;
-
         lock (_convLock)
         {
             var session = ChatSession;
-            _chatEngine.CommitAssistantMessage(session, conv, runTab, assistantContent, _storage);
+            assistantContent = _chatEngine.FinalizeAssistantTurn(session, conv, runTab, assistantContent, _storage);
             _currentConversation = session?.CurrentConversation ?? conv;
             conv = _currentConversation!;
         }
@@ -11022,13 +11018,10 @@ public partial class ChatWindow : Window
             SetStatusIdle();
         }
 
-        assistantContent = _chatEngine.NormalizeAssistantContent(conv, runTab, assistantContent);
-        if (runTab is "Cowork" or "Code")
-            conv.ShowExecutionHistory = false;
         lock (_convLock)
         {
             var session = ChatSession;
-            _chatEngine.CommitAssistantMessage(session, conv, runTab, assistantContent, _storage);
+            assistantContent = _chatEngine.FinalizeAssistantTurn(session, conv, runTab, assistantContent, _storage);
             _currentConversation = session?.CurrentConversation ?? conv;
             conv = _currentConversation!;
         }