fix: 修复asr 启动就初始化的问题

asrInstance.initialize 这个方法的作用是初始化阿里云 NUI SDK 的 ASR 实例。根据阿里云 SDK 的设计，这个初始化过程不仅仅是加载配置，它还会立即建立与云端的长连接（WebSocket），并进入一个“待命”状态。SDK 会请求打开音频设备。

延迟初始化，只在第一次需要时才进行初始化

lib/services/message_service.dart

@@ -60,23 +60,29 @@ class MessageService extends ChangeNotifier {
   Future<dynamic> _handleMethodCall(MethodCall call) async {
     switch (call.method) {
       case "onAsrResult":
-        replaceMessage(
-            id: _latestUserMessageId!, text: call.arguments, status: MessageStatus.normal);
-        break;
+        {
+          debugPrint("ASR 结果: ${call.arguments}");
+          replaceMessage(
+              id: _latestUserMessageId!, text: call.arguments, status: MessageStatus.normal);
+          break;
+        }
       case "onAsrStop":
-        int index = findMessageIndexById(_latestUserMessageId!);
-        if (index == -1) {
-          return;
+        {
+          debugPrint("ASR 停止: ${call.arguments}");
+          int index = findMessageIndexById(_latestUserMessageId!);
+          if (index == -1) {
+            return;
+          }
+          final message = _messages[index];
+          if (message.text.isEmpty) {
+            removeMessageById(_latestUserMessageId!);
+            return;
+          }
+          if (_asrCompleter != null && !_asrCompleter!.isCompleted) {
+            _asrCompleter!.complete(messages.last.text);
+          }
+          break;
         }
-        final message = _messages[index];
-        if (message.text.isEmpty) {
-          removeMessageById(_latestUserMessageId!);
-          return;
-        }
-        if (_asrCompleter != null && !_asrCompleter!.isCompleted) {
-          _asrCompleter!.complete(messages.last.text);
-        }
-        break;
     }
   }