fix(ui): honor disabled hero animations

test/hero_animation_controller_test.dart

@@ -0,0 +1,62 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  testWidgets(
+    'HeroControllerScope.none reaches the MaterialApp root Navigator',
+    (tester) async {
+      final navigatorKey = GlobalKey<NavigatorState>();
+
+      await tester.pumpWidget(
+        MaterialApp(
+          navigatorKey: navigatorKey,
+          builder: (context, child) =>
+              HeroControllerScope.none(child: child ?? const SizedBox.shrink()),
+          home: const SizedBox.shrink(),
+        ),
+      );
+
+      final navigatorContext = navigatorKey.currentContext!;
+      final scope = navigatorContext
+          .getInheritedWidgetOfExactType<HeroControllerScope>();
+      expect(scope, isNotNull);
+      expect(scope!.controller, isNull);
+    },
+  );
+
+  testWidgets('removing an explicit HeroController detaches it', (
+    tester,
+  ) async {
+    final navigatorKey = GlobalKey<NavigatorState>();
+    final controller = MaterialApp.createMaterialHeroController();
+    var enabled = true;
+    late StateSetter setHostState;
+
+    await tester.pumpWidget(
+      MaterialApp(
+        home: HeroControllerScope.none(
+          child: StatefulBuilder(
+            builder: (context, setState) {
+              setHostState = setState;
+              return Navigator(
+                key: navigatorKey,
+                observers: [if (enabled) controller],
+                onGenerateRoute: (_) => MaterialPageRoute<void>(
+                  builder: (_) => const SizedBox.shrink(),
+                ),
+              );
+            },
+          ),
+        ),
+      ),
+    );
+
+    expect(controller.navigator, same(navigatorKey.currentState));
+
+    setHostState(() => enabled = false);
+    await tester.pump();
+
+    expect(controller.navigator, isNull);
+    controller.dispose();
+  });
+}