feat(ground-suite): add system glass themes

ground-suite/test/widget_test.dart

@@ -2,6 +2,8 @@ import 'package:flutter/material.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:ground_suite/app/app.dart';
+import 'package:ground_suite/app/app_shell.dart';
+import 'package:ground_suite/shared/widgets/glass_panel.dart';
 
 void main() {
   testWidgets('replay workspace keeps diagnostics distinct and read-only', (
@@ -10,6 +12,11 @@ void main() {
     await tester.pumpWidget(const ProviderScope(child: GroundSuiteApp()));
     await tester.pumpAndSettle();
 
+    final app = tester.widget<MaterialApp>(find.byType(MaterialApp));
+    expect(app.themeMode, ThemeMode.system);
+    expect(app.theme?.brightness, Brightness.light);
+    expect(app.darkTheme?.brightness, Brightness.dark);
+    expect(find.byType(GlassPanel), findsAtLeastNWidgets(1));
     expect(find.text('Observation only'), findsOneWidget);
     expect(find.text('Replay fixture'), findsAtLeastNWidgets(1));
     expect(find.text('Vehicle identity'), findsOneWidget);
@@ -18,6 +25,8 @@ void main() {
     await tester.pumpAndSettle();
 
     expect(find.text('Diagnostics'), findsAtLeastNWidgets(1));
+    await tester.tap(find.text('Errors'));
+    await tester.pumpAndSettle();
     expect(
       find.text('kaptan_drivers::lidar_lite_v3::error::Error::TransferFault'),
       findsOneWidget,
@@ -42,4 +51,18 @@ void main() {
       expect(tester.takeException(), isNull);
     },
   );
+
+  testWidgets('follows a dark system preference', (tester) async {
+    tester.binding.platformDispatcher.platformBrightnessTestValue =
+        Brightness.dark;
+    addTearDown(
+      tester.binding.platformDispatcher.clearPlatformBrightnessTestValue,
+    );
+
+    await tester.pumpWidget(const ProviderScope(child: GroundSuiteApp()));
+    await tester.pumpAndSettle();
+
+    final context = tester.element(find.byType(AppShell));
+    expect(Theme.of(context).brightness, Brightness.dark);
+  });
 }