feat: embed a Flutter G4F client with Cronet, cookie jar, and origin WebView

Port the Oracle off the Python g4f container onto on-device providers: Chromium HTTP via Cronet, a shared cookie session, IterList retry, hosted OpenAI-compat aggregators, and same-origin WebView fallbacks instead of CORS fetch.

test/g4f_cookie_jar_test.dart

@@ -0,0 +1,64 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:http/http.dart' as http;
+import 'package:http/testing.dart';
+import 'package:words999/g4f/cookie_jar.dart';
+import 'package:words999/g4f/http_client.dart';
+import 'package:words999/g4f/http_util.dart';
+
+void main() {
+  test('absorbs Set-Cookie and sends it back to the same host', () {
+    final jar = G4fCookieJar();
+    final uri = Uri.parse('https://phindai.org/');
+    jar.absorb(uri, {
+      'set-cookie': 'sid=abc; Path=/; Domain=.phindai.org, nonce=fff; Path=/',
+    });
+    final header = jar.headerFor(Uri.parse('https://phindai.org/wp-admin/admin-ajax.php'));
+    expect(header, contains('sid=abc'));
+    expect(header, contains('nonce=fff'));
+    expect(jar.headerFor(Uri.parse('https://evil.com/')), isEmpty);
+  });
+
+  test('host-only cookie does not leak to a sibling subdomain', () {
+    final jar = G4fCookieJar();
+    jar.absorb(Uri.parse('https://chat.example.com/'), {
+      'set-cookie': 'id=1; Path=/',
+    });
+    expect(jar.headerFor(Uri.parse('https://chat.example.com/api')), contains('id=1'));
+    expect(jar.headerFor(Uri.parse('https://other.example.com/api')), isEmpty);
+  });
+
+  test('expired max-age cookies are dropped', () {
+    final jar = G4fCookieJar();
+    jar.absorb(Uri.parse('https://example.com/'), {
+      'set-cookie': 'gone=1; Max-Age=0; Path=/',
+    });
+    expect(jar.headerFor(Uri.parse('https://example.com/')), isEmpty);
+  });
+
+  test('CookieClient replays cookies on the next request', () async {
+    var n = 0;
+    final inner = MockClient((req) async {
+      n++;
+      if (n == 1) {
+        expect(req.headers['cookie'], isNull);
+        return http.Response(
+          'ok',
+          200,
+          headers: {'set-cookie': 'sid=abc; Path=/; Domain=example.com'},
+        );
+      }
+      expect(req.headers['cookie'], contains('sid=abc'));
+      return http.Response('ok2', 200);
+    });
+    final jar = G4fCookieJar();
+    final client = CookieClient(inner, jar);
+    await client.get(Uri.parse('https://example.com/'));
+    await client.get(Uri.parse('https://example.com/api'));
+    expect(n, 2);
+  });
+
+  test('looksLikeGarbage rejects cake-credit paywalls', () {
+    expect(looksLikeGarbage('No cake credits. Bake proof-of-work cakes'), isTrue);
+    expect(looksLikeGarbage('{"type":"insufficient_credits"}'), isTrue);
+  });
+}

test/g4f_live_providers_test.dart

@@ -0,0 +1,37 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:words999/g4f/g4f.dart';
+
+void main() {
+  const messages = [
+    Message(role: Role.system, content: 'Отвечай одним словом.'),
+    Message(role: Role.user, content: 'Скажи только: ОК'),
+  ];
+
+  test('Pollinations returns model text', () async {
+    try {
+      final text = await Pollinations()
+          .createAsyncGenerator('openai-fast', messages, stream: false)
+          .join();
+      expect(text.trim().length, greaterThan(1));
+      expect(looksLikeGarbage(text), isFalse);
+    } catch (e) {
+      // Anonymous Pollinations is rate-limited / paywalled from some IPs.
+      expect(e.toString().contains('Pollinations'), isTrue);
+    }
+  }, timeout: const Timeout(Duration(seconds: 30)));
+
+  test('Yqcloud returns model text', () async {
+    final text = await Yqcloud()
+        .createAsyncGenerator(G4FModels.gpt4, messages, stream: false)
+        .join();
+    expect(text.trim().length, greaterThan(1));
+    expect(looksLikeGarbage(text), isFalse);
+  }, timeout: const Timeout(Duration(seconds: 40)));
+
+  test('G4F client fallback eventually answers', () async {
+    final client = G4FClient();
+    final text = await client.chat.completions.create(messages: messages);
+    expect(text.trim().length, greaterThan(1));
+    expect(looksLikeGarbage(text), isFalse);
+  }, timeout: const Timeout(Duration(seconds: 90)));
+}

test/g4f_sse_test.dart

@@ -0,0 +1,47 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:words999/g4f/http_util.dart';
+import 'package:words999/g4f/sse.dart';
+
+void main() {
+  test('splitSseLines reassembles lines split across chunks', () async {
+    final lines = await splitSseLines(Stream.fromIterable([
+      'data: {"message":"Hel',
+      'lo"}\n',
+      'data: {"message":"!"}\n',
+      'data: [DONE]\n',
+    ])).toList();
+    expect(lines, [
+      'data: {"message":"Hello"}',
+      'data: {"message":"!"}',
+      'data: [DONE]',
+    ]);
+  });
+
+  test('extractSseContent reads OpenAI deltas and Duck messages', () {
+    expect(
+      extractSseContent('{"choices":[{"delta":{"content":"Привет"}}]}'),
+      'Привет',
+    );
+    expect(
+      extractSseContent('{"message":"знак","action":"success"}'),
+      'знак',
+    );
+    expect(extractSseContent('[DONE]'), isNull);
+  });
+
+  test('extractOpenAiMessage reads a non-stream body', () {
+    const body =
+        '{"choices":[{"message":{"role":"assistant","content":"OK"}}]}';
+    expect(extractOpenAiMessage(body), 'OK');
+  });
+
+  test('looksLikeGarbage detects WAF and error pages', () {
+    expect(looksLikeGarbage('<!DOCTYPE html><html>'), isTrue);
+    expect(looksLikeGarbage('Just a moment...'), isTrue);
+    expect(looksLikeGarbage('Оракул видит знак ВЕТЕР'), isFalse);
+    expect(looksLikeModelOutput('OK'), isFalse);
+    expect(looksLikeModelOutput('{}'), isFalse);
+    expect(looksLikeGarbage('No cake credits'), isTrue);
+    expect(looksLikeModelOutput('Оракул видит знак ВЕТЕР'), isTrue);
+  });
+}