fix(nav): preserve HTPC escape behavior

Use Flutter's supported desktop application-exit API so the second root Back press closes Plezy on Windows. Preserve fullscreen when video player navigation is enabled while keeping fullscreen-first Escape behavior for normal desktop use.

close #1582

test/services/app_exit_service_test.dart

@@ -0,0 +1,24 @@
+import 'dart:ui' as ui;
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:plezy/services/app_exit_service.dart';
+
+void main() {
+  test('desktop exit uses the required application exit API', () async {
+    ui.AppExitType? requestedType;
+    int? requestedCode;
+
+    expect(
+      await AppExitService.requestExit(
+        exitApplicationForTesting: (exitType, exitCode) async {
+          requestedType = exitType;
+          requestedCode = exitCode;
+          return ui.AppExitResponse.exit;
+        },
+      ),
+      isTrue,
+    );
+    expect(requestedType, ui.AppExitType.required);
+    expect(requestedCode, 0);
+  });
+}

test/widgets/video_controls_test.dart

@@ -428,6 +428,7 @@ void main() {
       bool Function()? isChromePresented,
       Future<bool> Function()? exitFullscreenIfActive,
       bool physicalEscapeExitsFullscreen = true,
+      bool Function()? physicalEscapeExitsFullscreenProvider,
       VoidCallback? exitPlayer,
       VoidCallback? navigateHome,
       bool Function()? isActive,
@@ -438,7 +439,7 @@ void main() {
         dismissPrompt: dismissPrompt ?? () {},
         isChromePresented: isChromePresented ?? () => chromeController.controlsPresented,
         exitFullscreenIfActive: exitFullscreenIfActive ?? () async => false,
-        physicalEscapeExitsFullscreen: physicalEscapeExitsFullscreen,
+        physicalEscapeExitsFullscreen: physicalEscapeExitsFullscreenProvider ?? () => physicalEscapeExitsFullscreen,
         exitPlayer: exitPlayer ?? () {},
         navigateHome: navigateHome ?? () {},
         isActive: isActive,
@@ -557,6 +558,31 @@ void main() {
       expect(exits, 0);
     });
 
+    testWidgets('enabling player navigation makes physical Escape preserve fullscreen', (tester) async {
+      final chromeController = PlayerChromeController();
+      addTearDown(chromeController.dispose);
+      var physicalEscapeExitsFullscreen = true;
+      var fullscreenChecks = 0;
+      var exits = 0;
+      final coordinator = coordinatorFor(
+        chromeController,
+        exitFullscreenIfActive: () async {
+          fullscreenChecks++;
+          return true;
+        },
+        physicalEscapeExitsFullscreenProvider: () => physicalEscapeExitsFullscreen,
+        exitPlayer: () => exits++,
+      );
+      physicalEscapeExitsFullscreen = false;
+      await pumpNavigationFocus(tester, coordinator);
+
+      await tester.sendKeyEvent(LogicalKeyboardKey.escape);
+
+      expect(fullscreenChecks, 0);
+      expect(chromeController.controlsVisible, isFalse);
+      expect(exits, 0);
+    });
+
     testWidgets('macOS physical Escape stages through chrome and player without leaving fullscreen', (tester) async {
       final chromeController = PlayerChromeController();
       addTearDown(chromeController.dispose);
@@ -705,6 +731,20 @@ void main() {
     });
   });
 
+  group('shouldPhysicalEscapeExitFullscreen', () {
+    test('uses fullscreen-first behavior for normal Windows and Linux navigation', () {
+      expect(shouldPhysicalEscapeExitFullscreen(isMacOS: false, videoPlayerNavigationEnabled: false), isTrue);
+    });
+
+    test('preserves fullscreen when HTPC-style player navigation is enabled', () {
+      expect(shouldPhysicalEscapeExitFullscreen(isMacOS: false, videoPlayerNavigationEnabled: true), isFalse);
+    });
+
+    test('preserves native fullscreen inside the macOS player', () {
+      expect(shouldPhysicalEscapeExitFullscreen(isMacOS: true, videoPlayerNavigationEnabled: false), isFalse);
+    });
+  });
+
   group('SkipMarkerButton', () {
     testWidgets('tap activates skip', (tester) async {
       final focusNode = FocusNode();