test: fix gamma default + localized home

Two tests asserted pre-refactor behavior:
- pen_config_test expected the old pressureGamma default of 1.0; it is
  now the natural curve (the pen-feel feature). Also assert the new
  eraser defaults.
- widget_test pumped HomeScreen without localization delegates, which
  the now-localized app bar requires. Provide the delegates.

Full suite: 258/258 pass.

test/pen_config_test.dart

@@ -7,6 +7,8 @@ import 'package:flutter_test/flutter_test.dart';
 import 'package:badnote/editor/engine/stroke_geometry.dart'
     show kDefaultPenThinning;
 import 'package:badnote/editor/input/pen_config.dart';
+import 'package:badnote/editor/input/pressure_curve.dart'
+    show kNaturalPressureGamma;
 
 void main() {
   group('applyPressureCurve', () {
@@ -56,7 +58,8 @@ void main() {
       final restored = PenConfig.fromJson({});
       expect(restored.sideButton, PenButtonAction.eraser);
       expect(restored.eraserEnd, PenButtonAction.eraser);
-      expect(restored.pressureGamma, 1.0);
+      // Default gamma is the natural pen curve (<1) — the rnote-like feel.
+      expect(restored.pressureGamma, kNaturalPressureGamma);
       expect(restored.palmRejectionMs, 150.0);
       expect(restored.fingerDrawing, false);
       expect(restored.penWidth, 0.004);
@@ -64,6 +67,9 @@ void main() {
       // Missing pressureSensitivity defaults to the shared thinning constant,
       // preserving the pre-existing stroke feel + export golden (plan M4).
       expect(restored.pressureSensitivity, kDefaultPenThinning);
+      // Eraser defaults: legacy fixed radius + segment (not whole-stroke) mode.
+      expect(restored.eraserRadius, kDefaultEraserRadius);
+      expect(restored.eraserWholeStroke, false);
     });
 
     test('fromJson falls back to defaults for unknown enum names', () {

test/widget_test.dart

@@ -3,6 +3,7 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:shared_preferences/shared_preferences.dart';
 
+import 'package:badnote/l10n/app_localizations.dart';
 import 'package:badnote/screens/home_screen.dart';
 
 void main() {
@@ -17,7 +18,14 @@ void main() {
     SharedPreferences.setMockInitialValues({});
 
     await tester.pumpWidget(
-      const ProviderScope(child: MaterialApp(home: HomeScreen())),
+      ProviderScope(
+        child: MaterialApp(
+          // The screen is now localized; provide the delegates it depends on.
+          localizationsDelegates: AppLocalizations.localizationsDelegates,
+          supportedLocales: AppLocalizations.supportedLocales,
+          home: const HomeScreen(),
+        ),
+      ),
     );
     await tester.pump();