feat: 原生支持 /v1/responses 接口与 Chat Completions 双协议自适应，增加端到端联调测试

kouyu_english/test/ai_config_test.dart

@@ -6,7 +6,7 @@ import 'package:kouyu_english/core/models.dart';
 void main() {
   TestWidgetsFlutterBinding.ensureInitialized();
 
-  group('AiService resolveEndpointUri (/v1/chat/completions)', () {
+  group('AiService resolveEndpointUri', () {
     test('resolves OpenAI endpoint ending in /v1 to /v1/chat/completions', () {
       final uri = AiService.resolveEndpointUri(
         provider: AiProviderType.openAi,
@@ -43,13 +43,13 @@ void main() {
       expect(uri.toString(), equals('https://codex.slcydia.fun/v1/chat/completions'));
     });
 
-    test('converts /responses endpoint to /chat/completions', () {
+    test('preserves /responses endpoint for OpenAI Responses API support', () {
       final uri = AiService.resolveEndpointUri(
         provider: AiProviderType.compatible,
         endpoint: 'https://codex.slcydia.fun/v1/responses',
         model: 'gpt-4o-mini',
       );
-      expect(uri.toString(), equals('https://codex.slcydia.fun/v1/chat/completions'));
+      expect(uri.toString(), equals('https://codex.slcydia.fun/v1/responses'));
     });
 
     test('resolves Gemini endpoint to :generateContent', () {

kouyu_english/test/live_endpoint_test.dart

@@ -0,0 +1,55 @@
+import 'dart:io';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:kouyu_english/core/ai_service.dart';
+import 'package:kouyu_english/core/models.dart';
+
+class RealHttpOverrides extends HttpOverrides {
+  @override
+  HttpClient createHttpClient(SecurityContext? context) {
+    return super.createHttpClient(context);
+  }
+}
+
+void main() {
+  TestWidgetsFlutterBinding.ensureInitialized();
+  HttpOverrides.global = RealHttpOverrides();
+  const testKey = '***REMOVED***';
+  AiService.instance.setFallbackApiKey(testKey);
+
+  test('Live test: /v1/responses endpoint testConnection', () async {
+    final resResponses = await AiService.instance.testConnection(
+      provider: AiProviderType.compatible,
+      endpoint: 'https://codex.slcydia.fun/v1/responses',
+      model: 'gemini-3.7-flash-high',
+      explicitApiKey: testKey,
+    );
+    print('Responses API result: ok=${resResponses.ok}, msg=${resResponses.message}');
+    expect(resResponses.ok, isTrue);
+  });
+
+  test('Live test: /v1 (Chat Completions) endpoint testConnection', () async {
+    final resChat = await AiService.instance.testConnection(
+      provider: AiProviderType.compatible,
+      endpoint: 'https://codex.slcydia.fun/v1',
+      model: 'gemini-3.7-flash-high',
+      explicitApiKey: testKey,
+    );
+    print('Chat Completions API result: ok=${resChat.ok}, msg=${resChat.message}');
+    expect(resChat.ok, isTrue);
+  });
+
+  test('Live test: /v1/responses dialogueReply', () async {
+    final reply = await AiService.instance.dialogueReply(
+      provider: AiProviderType.compatible,
+      endpoint: 'https://codex.slcydia.fun/v1/responses',
+      model: 'gemini-3.7-flash-high',
+      history: [
+        {'role': 'user', 'content': 'Hello, my name is Alex.'}
+      ],
+      requiredTask: 'Greet learner and ask what is their name',
+    );
+    print('Dialogue reply from /v1/responses: reply="${reply?.reply}", slots=${reply?.slots}, suggestsComplete=${reply?.suggestsComplete}');
+    expect(reply, isNotNull);
+    expect(reply!.reply, isNotEmpty);
+  });
+}