fix(app): the phrase is never copied, codes leave the clipboard a minute later

The recovery phrase opens the account's keys; clipboard histories and
cloud clipboard sync would keep it beyond the app's reach. It is saved as
a file or written down. Recovery codes and an authenticator's key may be
copied, and the clipboard is emptied 60 s later if it still holds them;
they are no longer selectable, as the system's own copy wouldn't empty it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

packages/halkyon_app/test/password/widget/secret_clipboard_test.dart

@@ -0,0 +1,103 @@
+import 'package:flutter/services.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:halkyon_app/halkyon_app.dart';
+import 'package:halkyon_app/testing.dart';
+import 'package:material_ui/material_ui.dart';
+
+void main() {
+  /// What the system's clipboard holds.
+  String? clipboard;
+
+  /// Stands in for the system's clipboard for [tester].
+  void mockClipboard(WidgetTester tester) {
+    clipboard = null;
+    tester.binding.defaultBinaryMessenger.setMockMethodCallHandler(
+      SystemChannels.platform,
+      (call) async => switch (call.method) {
+        'Clipboard.setData' => () {
+          clipboard = (call.arguments as Map)['text'] as String?;
+          return null;
+        }(),
+        'Clipboard.getData' => {'text': clipboard},
+        _ => null,
+      },
+    );
+    addTearDown(
+      () => tester.binding.defaultBinaryMessenger.setMockMethodCallHandler(
+        SystemChannels.platform,
+        null,
+      ),
+    );
+  }
+
+  Future<void> pumpView(WidgetTester tester, Widget view) async {
+    tester.view.physicalSize = const Size(412, 1400);
+    tester.view.devicePixelRatio = 1;
+    addTearDown(tester.view.reset);
+    await tester.pumpWidget(
+      AppScope(
+        dependencies: TestAppDependencies(gateway: FakeAuthGateway()),
+        child: MaterialApp(
+          localizationsDelegates:
+              HalkyonAppLocalizations.localizationsDelegates,
+          supportedLocales: HalkyonAppLocalizations.supportedLocales,
+          home: Scaffold(body: SingleChildScrollView(child: view)),
+        ),
+      ),
+    );
+  }
+
+  group('copySecret', () {
+    testWidgets('clears the clipboard a minute later', (tester) async {
+      mockClipboard(tester);
+      await copySecret('ABCD-EFGH');
+      expect(clipboard, 'ABCD-EFGH');
+      await tester.pump(const Duration(seconds: 59));
+      expect(clipboard, 'ABCD-EFGH');
+      await tester.pump(const Duration(seconds: 1));
+      expect(clipboard, '');
+    });
+
+    testWidgets('leaves what was copied since', (tester) async {
+      mockClipboard(tester);
+      await copySecret('ABCD-EFGH');
+      clipboard = 'something else';
+      await tester.pump(secretClipboardLifetime);
+      expect(clipboard, 'something else');
+    });
+  });
+
+  testWidgets('the recovery phrase is saved, never copied', (tester) async {
+    mockClipboard(tester);
+    await pumpView(
+      tester,
+      const RecoveryPhraseView(
+        phrase:
+            'abandon abandon abandon abandon abandon abandon abandon abandon '
+            'abandon abandon abandon abandon abandon abandon abandon abandon '
+            'abandon abandon abandon abandon abandon abandon abandon art',
+      ),
+    );
+    expect(find.text('Copy'), findsNothing);
+    expect(find.text('Save as a file'), findsOneWidget);
+    expect(find.byType(SelectableText), findsNothing);
+  });
+
+  testWidgets('recovery codes are copied, and cleared a minute later', (
+    tester,
+  ) async {
+    mockClipboard(tester);
+    await pumpView(
+      tester,
+      const RecoveryCodesView(codes: ['AAAA-BBBB', 'CCCC-DDDD']),
+    );
+    expect(find.byType(SelectableText), findsNothing);
+    await tester.tap(find.text('Copy'));
+    await tester.pump();
+    expect(clipboard, 'AAAA-BBBB\nCCCC-DDDD');
+    await tester.pump(secretClipboardLifetime);
+    expect(clipboard, '');
+    // The snack bar's own time.
+    await tester.pumpAndSettle();
+  });
+}