feat(client/ios): iPad tablet 正式适配——断点≥900 对齐设计源 + tablet golden 回归闸

- form_factor 触屏 tablet 阈值 600→900,对齐 design/ui_kits/tablet(1180×820 横屏
  侧栏):iPad 横屏/12.9″竖屏走侧栏,标准/11″竖屏回落 mobile 底 Tab,避免双栏挤压
- form_factor_test 补全断点边界(900/899)与各 iPad 尺寸用例
- 新增 tablet_pages_golden_test:四视图×明暗×中英 12 张 golden,注入演示数据
  (6 节点/周流量/30 天用量)让 2 列网格与周柱满渲染,作回归闸
- design/CONTRACT.md:tablet 像素契约(取自 tabapp.jsx)+ 逐屏验收清单
- 真机 iPad mini 6 视觉签核通过;141 测试全绿

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

client/test/golden/tablet_pages_golden_test.dart

@@ -0,0 +1,153 @@
+// tablet_pages_golden_test.dart — iPad/tablet 整页 golden（连接/节点/统计/账户）
+//
+// 用 debugDefaultTargetPlatformOverride=iOS + 1180×820 surface 让 context.formFactor
+// 判定为 tablet（宽 ≥900），渲染 TabletShell 各页，对照 design/ui_kits/tablet/tabapp.jsx
+// 像素基准做保真校准 / 回归闸。注入演示数据(节点/用量/账户)让网格与柱图有内容；
+// 覆盖矩阵 = 四视图 × {light,dark} × {zh,en}。生成基准：flutter test --update-goldens。
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:pangolin_vpn/bridge/vpn_bridge_mock.dart';
+import 'package:pangolin_vpn/bridge/vpn_bridge_provider.dart';
+import 'package:pangolin_vpn/l10n/app_text.dart';
+import 'package:pangolin_vpn/models/me.dart';
+import 'package:pangolin_vpn/models/node.dart';
+import 'package:pangolin_vpn/models/usage_point.dart';
+import 'package:pangolin_vpn/pangolin_theme.dart';
+import 'package:pangolin_vpn/services/token_store.dart';
+import 'package:pangolin_vpn/shell/home_shell.dart';
+import 'package:pangolin_vpn/shell/tablet_shell.dart';
+import 'package:pangolin_vpn/state/account_providers.dart';
+import 'package:pangolin_vpn/state/app_providers.dart';
+import 'package:pangolin_vpn/state/auth_provider.dart';
+import 'package:pangolin_vpn/state/navigation_provider.dart';
+import 'package:pangolin_vpn/state/nodes_provider.dart';
+
+class _NullTokenStore implements TokenStore {
+  const _NullTokenStore();
+  @override
+  Future<void> saveTokens({required String access, required String refresh}) async {}
+  @override
+  Future<String?> loadAccessToken() async => null;
+  @override
+  Future<String?> loadRefreshToken() async => null;
+  @override
+  Future<void> clear() async {}
+  @override
+  Future<void> markOnboarded() async {}
+  @override
+  Future<bool> isOnboarded() async => true;
+  @override
+  Future<void> saveLastEmail(String email) async {}
+  @override
+  Future<String?> loadLastEmail() async => null;
+}
+
+// ── 演示数据（让网格/柱图/账户有内容；不依赖登录态与网络）─────────────
+const List<Node> _demoNodes = [
+  Node(code: 'HK', nameZh: '香港 · 流媒体', nameEn: 'Hong Kong', ping: 18, tag: NodeTag.streaming, host: 'hk', port: 443),
+  Node(code: 'TW', nameZh: '台北', nameEn: 'Taipei', ping: 28, host: 'tw', port: 443),
+  Node(code: 'JP', nameZh: '东京', nameEn: 'Tokyo', ping: 32, host: 'jp', port: 443),
+  Node(code: 'KR', nameZh: '首尔', nameEn: 'Seoul', ping: 38, host: 'kr', port: 443),
+  Node(code: 'SG', nameZh: '新加坡', nameEn: 'Singapore', ping: 45, tag: NodeTag.p2p, host: 'sg', port: 443),
+  Node(code: 'US', nameZh: '洛杉矶', nameEn: 'Los Angeles', ping: 120, host: 'us', port: 443),
+];
+
+const Me _demoMe = Me(
+  email: 'me@pangolin.vpn',
+  plan: 'free',
+  devicesUsed: 2,
+  devicesMax: 1,
+  quotaTodayMin: 6,
+  dataTodayGb: 1.2,
+  weeklyGb: [2.1, 3.4, 1.8, 4.6, 5.2, 6.1, 3.0],
+);
+
+final List<UsagePoint> _demoUsage = List.generate(30, (i) {
+  return UsagePoint(
+    date: '2026-06-${(i + 1).toString().padLeft(2, '0')}',
+    bytesUp: 120 * 1024 * 1024 + i * 7 * 1024 * 1024,
+    bytesDown: 900 * 1024 * 1024 + i * 31 * 1024 * 1024,
+    minutesUsed: 24 + (i % 5) * 11,
+  );
+});
+
+class _FakeNodesNotifier extends NodesNotifier {
+  @override
+  Future<List<Node>> build() async => _demoNodes;
+}
+
+class _FakeMeNotifier extends MeNotifier {
+  @override
+  Future<Me> build() async => _demoMe;
+}
+
+const Size _ipad = Size(1180, 820); // 对齐设计源 tabapp.jsx 内屏
+
+Future<void> _shoot(
+  WidgetTester tester,
+  NavView view,
+  String name, {
+  bool settle = true,
+  Brightness brightness = Brightness.light,
+  AppLang lang = AppLang.zh,
+}) async {
+  debugDefaultTargetPlatformOverride = TargetPlatform.iOS;
+  tester.view.physicalSize = _ipad;
+  tester.view.devicePixelRatio = 1.0;
+  addTearDown(tester.view.resetPhysicalSize);
+  addTearDown(tester.view.resetDevicePixelRatio);
+  try {
+    await tester.pumpWidget(ProviderScope(
+      overrides: [
+        tokenStoreProvider.overrideWithValue(const _NullTokenStore()),
+        vpnBridgeProvider.overrideWithValue(VpnBridgeMock()),
+        navViewProvider.overrideWith((ref) => view),
+        localeProvider.overrideWith((ref) => lang),
+        nodesProvider.overrideWith(_FakeNodesNotifier.new),
+        meProvider.overrideWith(_FakeMeNotifier.new),
+        usageProvider(30).overrideWith((ref) async => _demoUsage),
+      ],
+      child: MaterialApp(
+        debugShowCheckedModeBanner: false,
+        theme: brightness == Brightness.dark ? PangolinTheme.dark : PangolinTheme.light,
+        home: const HomeShell(),
+      ),
+    ));
+    if (settle) {
+      await tester.pumpAndSettle();
+    } else {
+      await tester.pump();
+      await tester.pump(const Duration(milliseconds: 300));
+    }
+    await expectLater(find.byType(TabletShell), matchesGoldenFile('goldens/$name.png'));
+  } finally {
+    debugDefaultTargetPlatformOverride = null;
+  }
+}
+
+void main() {
+  // 连接页 off 态含连接键虚线环静态，但稳妥起见用 settle:false（pump 固定帧）。
+  for (final lang in const [AppLang.zh, AppLang.en]) {
+    final l = lang == AppLang.zh ? 'zh' : 'en';
+    testWidgets('tablet 连接·light·$l',
+        (t) => _shoot(t, NavView.connect, 'tablet_connect_light_$l', settle: false, lang: lang));
+    testWidgets('tablet 节点·light·$l',
+        (t) => _shoot(t, NavView.servers, 'tablet_servers_light_$l', lang: lang));
+    testWidgets('tablet 统计·light·$l',
+        (t) => _shoot(t, NavView.stats, 'tablet_stats_light_$l', lang: lang));
+    testWidgets('tablet 账户·light·$l',
+        (t) => _shoot(t, NavView.account, 'tablet_account_light_$l', lang: lang));
+  }
+
+  // 深色覆盖（中文，验证暗主题各视图）。
+  testWidgets('tablet 连接·dark·zh',
+      (t) => _shoot(t, NavView.connect, 'tablet_connect_dark_zh', settle: false, brightness: Brightness.dark));
+  testWidgets('tablet 节点·dark·zh',
+      (t) => _shoot(t, NavView.servers, 'tablet_servers_dark_zh', brightness: Brightness.dark));
+  testWidgets('tablet 统计·dark·zh',
+      (t) => _shoot(t, NavView.stats, 'tablet_stats_dark_zh', brightness: Brightness.dark));
+  testWidgets('tablet 账户·dark·zh',
+      (t) => _shoot(t, NavView.account, 'tablet_account_dark_zh', brightness: Brightness.dark));
+}

client/test/responsive/form_factor_test.dart

@@ -15,12 +15,23 @@ Future<FormFactor> _ffAt(WidgetTester tester, Size size) async {
 }
 
 void main() {
-  testWidgets('iPad 竖屏(768) → tablet', (t) async {
-    expect(await _ffAt(t, const Size(768, 1024)), FormFactor.tablet);
-  });
+  // tablet 阈值 ≥900，对齐 iPad 设计源(横屏侧栏布局)。
   testWidgets('iPad 横屏(1024) → tablet', (t) async {
     expect(await _ffAt(t, const Size(1024, 768)), FormFactor.tablet);
   });
+  testWidgets('iPad 12.9″ 竖屏(1024) → tablet', (t) async {
+    expect(await _ffAt(t, const Size(1024, 1366)), FormFactor.tablet);
+  });
+  testWidgets('iPad 11″ 竖屏(834) → mobile(窄屏回落底 Tab)', (t) async {
+    expect(await _ffAt(t, const Size(834, 1194)), FormFactor.mobile);
+  });
+  testWidgets('iPad 标准竖屏(768) → mobile', (t) async {
+    expect(await _ffAt(t, const Size(768, 1024)), FormFactor.mobile);
+  });
+  testWidgets('断点边界:900 → tablet, 899 → mobile', (t) async {
+    expect(await _ffAt(t, const Size(900, 1200)), FormFactor.tablet);
+    expect(await _ffAt(t, const Size(899, 1200)), FormFactor.mobile);
+  });
   testWidgets('iPhone(390) → mobile', (t) async {
     expect(await _ffAt(t, const Size(390, 844)), FormFactor.mobile);
   });