feat(android): 添加 CH934X USB 转串口芯片支持

- 在 AndroidManifest.xml 中添加 USB Host 权限声明
- 集成 CH934X Android SDK 并通过反射调用原生功能
- 实现设备查找、串口读写、GPIO 和 Modem 控制功能
- 添加异常回调机制处理设备拔出等情况
- 提供 Stream 数据流支持实时串口数据监听
- 完善单元测试覆盖所有核心功能模块

example/test/widget_test.dart

@@ -1,27 +1,15 @@
-// This is a basic Flutter widget test.
-//
-// To perform an interaction with a widget in your test, use the WidgetTester
-// utility in the flutter_test package. For example, you can send tap and scroll
-// gestures. You can also use WidgetTester to find child widgets in the widget
-// tree, read text, and verify that the values of widget properties are correct.
+// 示例应用 Widget 测试,验证应用能正常构建出主入口。
 
+import 'package:ch934x_serial_example/main.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 
-import 'package:ch934x_serial_example/main.dart';
-
 void main() {
-  testWidgets('Verify Platform version', (WidgetTester tester) async {
-    // Build our app and trigger a frame.
-    await tester.pumpWidget(const MyApp());
+  testWidgets('App boots and shows the example title', (tester) async {
+    await tester.pumpWidget(const Ch934xSerialExampleApp());
+    await tester.pump();
 
-    // Verify that platform version is retrieved.
-    expect(
-      find.byWidgetPredicate(
-        (Widget widget) =>
-            widget is Text && widget.data!.startsWith('Running on:'),
-      ),
-      findsOneWidget,
-    );
+    expect(find.text('CH934X Serial Example'), findsWidgets);
+    expect(find.byType(MaterialApp), findsOneWidget);
   });
 }