fix: 修复特征提取失败(错误码81929)

问题: extractFaceFeature 返回错误码 81929 (MERR_FSDK_FACEFEATURE_FACEDATA)

根本原因: detectFaces 返回的人脸信息缺少 faceData 字段，
而虹软 SDK 的 extractFaceFeature 必须要有这个字段才能提取特征

修复:
- FaceEngineManager.convertFaceInfoToList: 添加返回 faceData
- ArcPlugin.handleExtractFaceFeature: 接收并传递 faceData 参数
- Dart API: extractFaceFeature 添加 faceData 参数
- example: 传递 faceData 到特征提取调用

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

lib/arc_method_channel.dart

@@ -0,0 +1,135 @@
+import 'package:flutter/foundation.dart';
+import 'package:flutter/services.dart';
+
+import 'arc_platform_interface.dart';
+
+/// An implementation of [ArcPlatform] that uses method channels.
+class MethodChannelArc extends ArcPlatform {
+  /// The method channel used to interact with the native platform.
+  @visibleForTesting
+  final methodChannel = const MethodChannel('arc');
+
+  @override
+  Future<String?> getPlatformVersion() async {
+    final version = await methodChannel.invokeMethod<String>('getPlatformVersion');
+    return version;
+  }
+
+  @override
+  Future<Map<String, dynamic>?> activeOnline({
+    required String appId,
+    required String sdkKey,
+    required String activeKey,
+  }) async {
+    final result = await methodChannel.invokeMethod<Map<dynamic, dynamic>>('activeOnline', {
+      'appId': appId,
+      'sdkKey': sdkKey,
+      'activeKey': activeKey,
+    });
+    return result?.cast<String, dynamic>();
+  }
+
+  @override
+  Future<Map<String, dynamic>?> init({
+    int? detectMode,
+    int? orient,
+    int? maxFaceNum,
+    int? combinedMask,
+  }) async {
+    final result = await methodChannel.invokeMethod<Map<dynamic, dynamic>>('init', {
+      'detectMode': detectMode,
+      'orient': orient,
+      'maxFaceNum': maxFaceNum,
+      'combinedMask': combinedMask,
+    });
+    return result?.cast<String, dynamic>();
+  }
+
+  @override
+  Future<Map<String, dynamic>?> detectFaces({
+    required Uint8List data,
+    required int width,
+    required int height,
+    int format = 2050,
+  }) async {
+    final result = await methodChannel.invokeMethod<Map<dynamic, dynamic>>('detectFaces', {
+      'data': data,
+      'width': width,
+      'height': height,
+      'format': format,
+    });
+    return result?.cast<String, dynamic>();
+  }
+
+  @override
+  Future<Map<String, dynamic>?> extractFaceFeature({
+    required Uint8List data,
+    required int width,
+    required int height,
+    required int rectLeft,
+    required int rectTop,
+    required int rectRight,
+    required int rectBottom,
+    int format = 2050,
+    int faceOrientation = 0,
+    int faceId = -1,
+    Uint8List? faceData,
+    int extractType = 1,
+    int mask = 0,
+  }) async {
+    final result = await methodChannel.invokeMethod<Map<dynamic, dynamic>>('extractFaceFeature', {
+      'data': data,
+      'width': width,
+      'height': height,
+      'format': format,
+      'rectLeft': rectLeft,
+      'rectTop': rectTop,
+      'rectRight': rectRight,
+      'rectBottom': rectBottom,
+      'faceOrientation': faceOrientation,
+      'faceId': faceId,
+      'faceData': faceData,  // 关键：传递 faceData，这是虹软 SDK 特征提取必需的数据
+      'extractType': extractType,
+      'mask': mask,
+    });
+    return result?.cast<String, dynamic>();
+  }
+
+  @override
+  Future<Map<String, dynamic>?> compareFaceFeature({
+    required Uint8List featureData1,
+    required Uint8List featureData2,
+    int compareModel = 0,
+  }) async {
+    final result = await methodChannel.invokeMethod<Map<dynamic, dynamic>>('compareFaceFeature', {
+      'featureData1': featureData1,
+      'featureData2': featureData2,
+      'compareModel': compareModel,
+    });
+    return result?.cast<String, dynamic>();
+  }
+
+  @override
+  Future<Map<String, dynamic>?> registerFaceFeature({
+    required int searchId,
+    required Uint8List featureData,
+    String? faceTag,
+  }) async {
+    final result = await methodChannel.invokeMethod<Map<dynamic, dynamic>>('registerFaceFeature', {
+      'searchId': searchId,
+      'featureData': featureData,
+      'faceTag': faceTag,
+    });
+    return result?.cast<String, dynamic>();
+  }
+
+  @override
+  Future<Map<String, dynamic>?> registerFaceFeatureBatch({
+    required List<Map<String, dynamic>> faceList,
+  }) async {
+    final result = await methodChannel.invokeMethod<Map<dynamic, dynamic>>('registerFaceFeatureBatch', {
+      'faceList': faceList,
+    });
+    return result?.cast<String, dynamic>();
+  }
+}