fix(mobile): suppress failure callbacks for intentional auth cancellation

Signed-off-by: Tom Brow <tomb@block.xyz>

mobile/lib/shared/relay/relay_socket.dart

@@ -16,6 +16,10 @@ import 'nostr_models.dart';
 /// Does NOT handle reconnection — that is [RelaySessionNotifier]'s job.
 enum SocketState { disconnected, connecting, authenticating, connected }
 
+class _RelayDisconnectCancelled implements Exception {
+  const _RelayDisconnectCancelled();
+}
+
 class RelayAuthRejectedException implements Exception {
   final String message;
 
@@ -129,7 +133,7 @@ class RelaySocket {
     } catch (e) {
       _authTimeout?.cancel();
       await disconnect();
-      _onDisconnected(e);
+      if (e is! _RelayDisconnectCancelled) _onDisconnected(e);
     }
   }
 
@@ -140,7 +144,7 @@ class RelaySocket {
 
   /// Gracefully close the connection.
   Future<void> disconnect() async {
-    _failAuth(Exception('Relay disconnected during authentication'));
+    _failAuth(const _RelayDisconnectCancelled());
     _resetConnection();
     final channel = _channel;
     _channel = null;

mobile/test/shared/relay/relay_socket_liveness_test.dart

@@ -56,6 +56,7 @@ void main() {
     RelaySocket.debugPingInterval = RelaySocket.pingInterval;
     final server = await HttpServer.bind(InternetAddress.loopbackIPv4, 0);
     final authReceived = Completer<void>();
+    final disconnectErrors = <Object?>[];
     WebSocket? peer;
     server.listen((request) async {
       final connection = await WebSocketTransformer.upgrade(request);
@@ -73,7 +74,7 @@ void main() {
       nsec: nostr.Keys.generate().nsec,
       onMessage: (_) {},
       onConnected: () => fail('The peer never acknowledges authentication'),
-      onDisconnected: (_) {},
+      onDisconnected: disconnectErrors.add,
     );
     final connecting = socket.connect();
     try {
@@ -82,6 +83,7 @@ void main() {
       await socket.disconnect();
       await connecting.timeout(const Duration(seconds: 1));
       expect(socket.state, SocketState.disconnected);
+      expect(disconnectErrors, isEmpty);
     } finally {
       socket.dispose();
       await peer?.close();