fix(ui): keep three extension columns at default width

ui/flutter/lib/features/extensions/presentation/pages/extensions_page.dart

@@ -27,7 +27,7 @@ import '../widgets/extension_detail_view.dart';
 import '../widgets/extension_icon.dart';
 import '../widgets/extension_setting_field.dart';
 
-const _extensionCardMinWidth = 296.0;
+const _extensionCardMinWidth = 290.0;
 const _extensionGridSpacing = 10.0;
 
 int _extensionGridColumnCount(double width) {

ui/flutter/test/widget_test.dart

@@ -504,6 +504,11 @@ void main() {
       closeTo(tester.getRect(find.byKey(const ValueKey('extension-card-extension-2'))).right, 0.01),
     );
 
+    tester.view.physicalSize = const Size(1024, 768);
+    await tester.pumpAndSettle();
+    expect(gridColumns(), 3);
+    expect(tester.getSize(find.byKey(const ValueKey('extension-card-extension-0'))).width, greaterThanOrEqualTo(290));
+
     tester.view.physicalSize = const Size(1028, 608);
     await tester.pumpAndSettle();
     expect(gridColumns(), 3);