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/handlers/SessionMessageHandler.ts

@@ -25,6 +25,8 @@ export class SessionMessageHandler extends BaseMessageHandler {
       'getQwenSessions',
       'saveSession',
       'resumeSession',
+      // UI action: open a new chat tab (new WebviewPanel)
+      'openNewChatTab',
     ].includes(messageType);
   }
 
@@ -82,6 +84,24 @@ export class SessionMessageHandler extends BaseMessageHandler {
         await this.handleResumeSession((data?.sessionId as string) || '');
         break;
 
+      case 'openNewChatTab':
+        // Open a brand new chat tab (WebviewPanel) via the extension command
+        // This does not alter the current conversation in this tab; the new tab
+        // will initialize its own state and (optionally) create a new session.
+        try {
+          await vscode.commands.executeCommand('qwenCode.openNewChatTab');
+        } catch (error) {
+          console.error(
+            '[SessionMessageHandler] Failed to open new chat tab:',
+            error,
+          );
+          this.sendToWebView({
+            type: 'error',
+            data: { message: `Failed to open new chat tab: ${error}` },
+          });
+        }
+        break;
+
       default:
         console.warn(
           '[SessionMessageHandler] Unknown message type:',