fix: signature fallback retries connect, SSH tunnel auto-restart (closes #131, #132)

#131: Store challenge nonce and re-send connect message after advancing
signature mode on 'device signature invalid' rejection. Previously the
client got stuck in Connecting state after mode fallback.

#132: Clean up process/spec on unexpected SSH tunnel exit, raise
TunnelExited event. App.xaml.cs subscribes and auto-restarts after 3s
delay. Previously the tunnel stayed dead until manual intervention.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/OpenClaw.Shared/OpenClawGatewayClient.cs

@@ -53,6 +53,7 @@ public class OpenClawGatewayClient : WebSocketClientBase
     private string _connectAuthToken;
     private SignatureTokenMode _signatureTokenMode = SignatureTokenMode.V3AuthToken;
     private long? _challengeTimestampMs;
+    private string? _currentChallengeNonce;
     private bool _usageStatusUnsupported;
     private bool _usageCostUnsupported;
     private bool _sessionPreviewUnsupported;
@@ -788,6 +789,7 @@ public class OpenClawGatewayClient : WebSocketClientBase
             if (_signatureTokenMode != previousMode)
             {
                 _logger.Warn($"Gateway rejected device signature with mode {previousMode}; retrying with mode {_signatureTokenMode}");
+                _ = SendConnectMessageAsync(_currentChallengeNonce);
                 return;
             }
 
@@ -1125,6 +1127,7 @@ public class OpenClawGatewayClient : WebSocketClientBase
         }
 
         _challengeTimestampMs = ts;
+        _currentChallengeNonce = nonce;
         
         _logger.Info($"Received challenge, nonce: {nonce}");
         _ = SendConnectMessageAsync(nonce);

src/OpenClaw.Tray.WinUI/App.xaml.cs

@@ -270,6 +270,7 @@ public partial class App : Application
         ToastNotificationManagerCompat.OnActivated += OnToastActivated;
 
         _sshTunnelService = new SshTunnelService(new AppLogger());
+        _sshTunnelService.TunnelExited += OnSshTunnelExited;
 
         // First-run check
         if (string.IsNullOrWhiteSpace(_settings.Token))
@@ -2264,7 +2265,25 @@ public partial class App : Application
 
     #endregion
 
-    private Microsoft.UI.Dispatching.DispatcherQueue? AppDispatcherQueue => 
+    private async void OnSshTunnelExited(object? sender, int exitCode)
+    {
+        Logger.Warn($"SSH tunnel exited unexpectedly (code {exitCode}); restarting in 3s...");
+        await Task.Delay(3000);
+        if (_sshTunnelService != null && _settings?.UseSshTunnel == true)
+        {
+            try
+            {
+                _sshTunnelService.EnsureStarted(_settings);
+                Logger.Info("SSH tunnel restarted successfully");
+            }
+            catch (Exception ex)
+            {
+                Logger.Error($"SSH tunnel restart failed: {ex.Message}");
+            }
+        }
+    }
+
+    private Microsoft.UI.Dispatching.DispatcherQueue? AppDispatcherQueue =>
         Microsoft.UI.Dispatching.DispatcherQueue.GetForCurrentThread();
 }
 

src/OpenClaw.Tray.WinUI/Services/SshTunnelService.cs

@@ -16,6 +16,9 @@ public sealed class SshTunnelService : IDisposable
     private string? _lastSpec;
     private bool _stopping;
 
+    /// <summary>Raised when the SSH tunnel exits unexpectedly (not during shutdown).</summary>
+    public event EventHandler<int>? TunnelExited;
+
     public SshTunnelService(IOpenClawLogger logger)
     {
         _logger = logger;
@@ -130,6 +133,10 @@ public sealed class SshTunnelService : IDisposable
             else
             {
                 _logger.Warn($"SSH tunnel exited unexpectedly (code {exitCode})");
+                try { process.Dispose(); } catch { }
+                _process = null;
+                _lastSpec = null;
+                TunnelExited?.Invoke(this, exitCode);
             }
         };