refactor(vscode): 重构消息排序和展示逻辑

- 移除旧的消息排序改进总结文档
- 重新组织消息渲染逻辑，合并所有类型的消息按时间戳排序
- 优化工具调用处理流程，添加时间戳支持
- 改进会话保存机制，直接使用SessionManager保存检查点
- 重构部分组件以提高可维护性

packages/vscode-ide-companion/src/webview/components/layouts/ChatHeader.tsx

@@ -48,31 +48,6 @@ export const ChatHeader: React.FC<ChatHeaderProps> = ({
     {/* Spacer */}
     <div className="flex-1"></div>
 
-    {/* Save Session Button */}
-    {/* <button
-        className="flex-none p-0 bg-transparent border border-transparent rounded cursor-pointer flex items-center justify-center outline-none w-6 h-6 hover:bg-[var(--app-ghost-button-hover-background)] focus:bg-[var(--app-ghost-button-hover-background)]"
-        style={{
-          color: 'var(--app-primary-foreground)',
-        }}
-        onClick={onSaveSession}
-        title="Save Conversation"
-      >
-        <svg
-          xmlns="http://www.w3.org/2000/svg"
-          viewBox="0 0 20 20"
-          fill="currentColor"
-          aria-hidden="true"
-          data-slot="icon"
-          className="w-4 h-4"
-        >
-          <path
-            fillRule="evenodd"
-            d="M4.25 2A2.25 2.25 0 0 0 2 4.25v11.5A2.25 2.25 0 0 0 4.25 18h11.5A2.25 2.25 0 0 0 18 15.75V8.25a.75.75 0 0 1 .217-.517l.083-.083a.75.75 0 0 1 1.061 0l2.239 2.239A.75.75 0 0 1 22 10.5v5.25a4.75 4.75 0 0 1-4.75 4.75H4.75A4.75 4.75 0 0 1 0 15.75V4.25A4.75 4.75 0 0 1 4.75 0h5a.75.75 0 0 1 0 1.5h-5ZM9.017 6.5a1.5 1.5 0 0 1 2.072.58l.43.862a1 1 0 0 0 .895.558h3.272a1.5 1.5 0 0 1 1.5 1.5v6.75a1.5 1.5 0 0 1-1.5 1.5h-7.5a1.5 1.5 0 0 1-1.5-1.5v-6.75a1.5 1.5 0 0 1 1.5-1.5h1.25a1 1 0 0 0 .895-.558l.43-.862a1.5 1.5 0 0 1 .511-.732ZM11.78 8.47a.75.75 0 0 0-1.06-1.06L8.75 9.379 7.78 8.41a.75.75 0 0 0-1.06 1.06l1.5 1.5a.75.75 0 0 0 1.06 0l2.5-2.5Z"
-            clipRule="evenodd"
-          ></path>
-        </svg>
-      </button> */}
-
     {/* New Session Button */}
     <button
       className="flex-none p-0 bg-transparent border border-transparent rounded cursor-pointer flex items-center justify-center outline-none w-6 h-6 hover:bg-[var(--app-ghost-button-hover-background)] focus:bg-[var(--app-ghost-button-hover-background)]"