fix(ui): preserve desktop platform listeners (#1483)

ui/flutter/test/app/application/app_platform_controller_test.dart

@@ -0,0 +1,88 @@
+import 'dart:async';
+
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:gopeed/api/model/downloader_config.dart';
+import 'package:gopeed/app/application/app_platform_controller.dart';
+import 'package:gopeed/app/application/app_runtime_controller.dart';
+import 'package:gopeed/core/common/api_server_state.dart';
+import 'package:gopeed/core/common/start_config.dart';
+import 'package:gopeed/util/updater.dart';
+
+void main() {
+  test('runtime updates do not rebuild the platform controller', () async {
+    final container = ProviderContainer(
+      overrides: [
+        appRuntimeControllerProvider.overrideWith(_TestRuntimeController.new),
+        appPlatformControllerProvider.overrideWith(_TestPlatformController.new),
+      ],
+    );
+    addTearDown(container.dispose);
+    final subscription = container.listen(appPlatformControllerProvider, (_, _) {}, fireImmediately: true);
+    addTearDown(subscription.close);
+
+    await container.read(appPlatformControllerProvider.future);
+    final platformController = container.read(appPlatformControllerProvider.notifier) as _TestPlatformController;
+    final runtimeController = container.read(appRuntimeControllerProvider.notifier) as _TestRuntimeController;
+
+    expect(platformController.buildCount, 1);
+
+    runtimeController.completeRuntime();
+    await container.read(appRuntimeControllerProvider.future);
+    await Future<void>.delayed(Duration.zero);
+    expect(platformController.updateCheckCount, 1);
+
+    final config = DownloaderConfig.fromJson(runtimeController.state.requireValue.downloaderConfig.toJson());
+    config.extra.locale = 'zh';
+    runtimeController.replaceDownloaderConfig(config);
+    await container.pump();
+
+    expect(platformController.buildCount, 1);
+  });
+}
+
+class _TestPlatformController extends AppPlatformController {
+  int buildCount = 0;
+  int updateCheckCount = 0;
+
+  @override
+  bool get isDesktop => false;
+
+  @override
+  Future<AppPlatformState> build() {
+    buildCount++;
+    return super.build();
+  }
+
+  @override
+  Future<VersionInfo?> checkForUpdate() async {
+    updateCheckCount++;
+    return null;
+  }
+}
+
+class _TestRuntimeController extends AppRuntimeController {
+  final _pendingRuntime = Completer<AppRuntimeState>();
+
+  @override
+  Future<AppRuntimeState> build() => _pendingRuntime.future;
+
+  void completeRuntime() {
+    _pendingRuntime.complete(
+      AppRuntimeState(
+        startConfig: StartConfig(),
+        apiServerState: const ApiServerState(
+          enabled: false,
+          mcpEnabled: false,
+          running: false,
+          network: '',
+          address: '',
+          runningPort: 0,
+          pendingApply: false,
+          lastError: '',
+        ),
+        downloaderConfig: DownloaderConfig(),
+      ),
+    );
+  }
+}