feat: 重构 Home Screen 视觉设计与消息输入组件

- 新增 Home Screen 视觉设计 token (背景、工具栏、对话区、输入框等)
- 重构首页布局为浮动式底部输入栈结构
- 新增 HomeBackgroundField、HomeFloatingHeader、HomeAttachmentStrip 组件
- 优化 MessageComposer 视觉样式为悬浮 shell 设计
- 添加相关测试用例

apps/test/features/home/ui/widgets/home_background_field_test.dart

@@ -0,0 +1,17 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:social_app/features/home/ui/widgets/home_background_field.dart';
+
+void main() {
+  testWidgets('home background field renders layered glow surfaces', (
+    tester,
+  ) async {
+    await tester.pumpWidget(
+      const MaterialApp(home: Scaffold(body: HomeBackgroundField())),
+    );
+
+    expect(find.byKey(homeBackgroundFieldKey), findsOneWidget);
+    expect(find.byKey(homeTopGlowKey), findsOneWidget);
+    expect(find.byKey(homeBottomGlowKey), findsOneWidget);
+  });
+}

apps/test/features/home/ui/widgets/home_composer_test.dart

@@ -2,6 +2,7 @@ import 'package:flutter/gestures.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:lucide_icons/lucide_icons.dart';
+import 'package:social_app/core/theme/design_tokens.dart';
 import 'package:social_app/shared/widgets/message_composer.dart';
 
 Widget _buildTestApp({
@@ -50,8 +51,11 @@ void main() {
       );
 
       expect(find.byKey(messageComposerContainerKey), findsOneWidget);
+      expect(find.byKey(messageComposerShellKey), findsOneWidget);
+      expect(find.byKey(messageComposerInnerKey), findsOneWidget);
 
       final containerFinder = find.byKey(messageComposerContainerKey);
+      final shellFinder = find.byKey(messageComposerShellKey);
       final plusFinder = find.byKey(messageComposerPlusButtonKey);
       final rightFinder = find.byKey(messageComposerRightButtonKey);
 
@@ -63,6 +67,29 @@ void main() {
         find.descendant(of: containerFinder, matching: rightFinder),
         findsOneWidget,
       );
+
+      final container = tester.widget<Container>(shellFinder);
+      final decoration = container.decoration! as BoxDecoration;
+      expect(decoration.color, AppColors.homeComposerShell);
+      expect(
+        (decoration.border! as Border).top.color,
+        AppColors.homeComposerBorder,
+      );
+    });
+
+    testWidgets('recording state keeps unified floating shell', (tester) async {
+      await tester.pumpWidget(
+        _buildTestApp(
+          mode: MessageComposerMode.holdToSpeak,
+          process: MessageComposerProcess.recording,
+          hasMessage: false,
+          isWaitingAgent: false,
+        ),
+      );
+
+      expect(find.byKey(messageComposerShellKey), findsOneWidget);
+      expect(find.byKey(messageComposerInnerKey), findsOneWidget);
+      expect(find.text('松开发送'), findsOneWidget);
     });
 
     testWidgets('right action icon follows state priority', (tester) async {
@@ -85,7 +112,9 @@ void main() {
           of: find.byKey(messageComposerRightButtonKey),
           matching: find.byType(Icon),
         );
+        expect(iconFinder, findsOneWidget);
         final iconWidget = tester.widget<Icon>(iconFinder.first);
+        expect(iconWidget.icon, isNotNull);
         return iconWidget.icon!;
       }
 

apps/test/features/home/ui/widgets/home_screen_layout_test.dart

@@ -0,0 +1,112 @@
+import 'package:dio/dio.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:image_picker/image_picker.dart';
+import 'package:social_app/core/api/i_api_client.dart';
+import 'package:social_app/core/di/injection.dart';
+import 'package:social_app/features/chat/presentation/bloc/chat_bloc.dart';
+import 'package:social_app/features/home/ui/screens/home_screen.dart';
+import 'package:social_app/features/home/ui/widgets/home_attachment_strip.dart';
+import 'package:social_app/features/home/ui/widgets/home_floating_header.dart';
+import 'package:social_app/features/messages/data/inbox_api.dart';
+
+class _TestApiClient implements IApiClient {
+  @override
+  Future<Response<T>> delete<T>(String path, {data, Options? options}) async {
+    return Response<T>(requestOptions: RequestOptions(path: path));
+  }
+
+  @override
+  Future<Response<T>> get<T>(String path, {Options? options}) async {
+    return Response<T>(
+      requestOptions: RequestOptions(path: path),
+      data: <dynamic>[] as T,
+    );
+  }
+
+  @override
+  Future<Stream<String>> getSseLines(
+    String path, {
+    Map<String, String>? headers,
+  }) async {
+    return const Stream<String>.empty();
+  }
+
+  @override
+  Future<Response<T>> patch<T>(String path, {data, Options? options}) async {
+    return Response<T>(requestOptions: RequestOptions(path: path));
+  }
+
+  @override
+  Future<Response<T>> post<T>(String path, {data, Options? options}) async {
+    return Response<T>(requestOptions: RequestOptions(path: path));
+  }
+}
+
+void main() {
+  late ChatBloc chatBloc;
+
+  setUp(() {
+    final apiClient = _TestApiClient();
+    if (sl.isRegistered<InboxApi>()) {
+      sl.unregister<InboxApi>();
+    }
+    sl.registerSingleton<InboxApi>(InboxApi(apiClient));
+    chatBloc = ChatBloc(apiClient: apiClient);
+  });
+
+  tearDown(() async {
+    await chatBloc.close();
+    if (sl.isRegistered<InboxApi>()) {
+      await sl.unregister<InboxApi>();
+    }
+  });
+
+  Future<void> pumpHomeScreen(
+    WidgetTester tester, {
+    List<XFile> initialSelectedImages = const [],
+  }) async {
+    await tester.pumpWidget(
+      MaterialApp(
+        home: HomeScreen(
+          chatBloc: chatBloc,
+          autoLoadHistory: false,
+          initialSelectedImages: initialSelectedImages,
+        ),
+      ),
+    );
+    await tester.pump();
+  }
+
+  testWidgets(
+    'home screen shows floating header, conversation stage, and bottom input stack',
+    (tester) async {
+      await pumpHomeScreen(tester);
+
+      expect(find.byKey(homeFloatingHeaderKey), findsOneWidget);
+      expect(find.byKey(homeConversationStageKey), findsOneWidget);
+      expect(find.byKey(homeBottomInputStackKey), findsOneWidget);
+    },
+  );
+
+  testWidgets('empty state keeps clean stage without helper copy', (
+    tester,
+  ) async {
+    await pumpHomeScreen(tester);
+
+    expect(find.byKey(homeConversationStageKey), findsOneWidget);
+    expect(find.byKey(homeEmptyStateAmbientKey), findsOneWidget);
+    expect(find.text('开始对话吧'), findsNothing);
+  });
+
+  testWidgets('selected images render in attachment strip above composer', (
+    tester,
+  ) async {
+    await pumpHomeScreen(
+      tester,
+      initialSelectedImages: [XFile('/tmp/mock-image-a.png')],
+    );
+
+    expect(find.byKey(homeAttachmentStripKey), findsOneWidget);
+  });
+}