feat(ui): 更新品牌启动页与选集交互

test/discover/home_all_dramas_grid_test.dart

@@ -148,6 +148,15 @@ void main() {
 
     expect(find.byKey(const Key('home-all-dramas-title')), findsNothing);
     expect(find.text('No matching dramas.'), findsOneWidget);
+    final content = tester.getCenter(
+      find.byKey(const Key('empty-state-content')),
+    );
+    final chipsBottom = tester
+        .getBottomLeft(find.byKey(const Key('home-category-chips')))
+        .dy;
+    final feed = tester.getRect(find.byType(CustomScrollView));
+    expect(content.dx, closeTo(feed.center.dx, 1));
+    expect(content.dy, closeTo((chipsBottom + feed.bottom) / 2, 36));
 
     await tester.tap(find.text('Romance'));
     await tester.pumpAndSettle();
@@ -168,6 +177,10 @@ void main() {
     expect(find.byKey(const Key('home-all-dramas-title')), findsNothing);
     expect(find.text('Categories could not be loaded.'), findsOneWidget);
     expect(find.text('Retry'), findsOneWidget);
+    expect(find.byKey(const Key('empty-state-icon')), findsOneWidget);
+    final icon = tester.getCenter(find.byKey(const Key('empty-state-icon')));
+    final feed = tester.getRect(find.byType(CustomScrollView));
+    expect(icon.dx, closeTo(feed.center.dx, 1));
     expect(find.byKey(const Key('home-all-dramas-grid')), findsNothing);
   });