showExistingAccountSwitchDialog function

@visibleForTesting Future<bool> showExistingAccountSwitchDialog(BuildContext context)

Confirms the destructive half of a guest-to-existing-account transition.

Kept as a separate function so the behavior is directly widget-testable and every caller presents the same warning before guest progress is abandoned.

Implementation

@visibleForTesting
Future<bool> showExistingAccountSwitchDialog(BuildContext context) async {
  return await showDialog<bool>(
        context: context,
        builder: (dialogContext) => AlertDialog(
          scrollable: true,
          title: const Text('Sign in to your existing account?'),
          content: const Text(
            'That Google account already exists. You can sign in to it, but '
            'this guest’s games, ratings, and friends cannot be transferred.',
          ),
          actions: [
            TextButton(
              onPressed: () => Navigator.pop(dialogContext, false),
              child: const Text('Keep playing as guest'),
            ),
            FilledButton(
              onPressed: () => Navigator.pop(dialogContext, true),
              child: const Text('Sign in'),
            ),
          ],
        ),
      ) ??
      false;
}