Skip browser retry after persistence-fallback recreation

After RecreateCredentialsWithoutPersistence() rebuilds both credentials,
CacheAuthenticationRecord retries Authenticate(). The retry was
re-entering the InteractiveBrowserCredential path even though the first
attempt had already proved the browser flow was unavailable in this
environment (the _isDeviceCodeFallback flag was set, but only
GetTokenCore checked it — Authenticate did not).

On headless WSL the browser credential opens a Windows-side browser
but the OAuth redirect to http://localhost:XXXX cannot reach the
WSL-side listener, so the second InteractiveBrowserCredential.Authenticate
call hangs forever. The device code prompt never gets a chance to
print.

Honor _isDeviceCodeFallback at the top of Authenticate so the second
call goes straight to DeviceCodeCredential. With this fix, "darc login"
on WSL prints the device code + URL immediately on the retry instead of
hanging.

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

Author: lewing

src/Maestro/Maestro.Common/AppCredentials/CachedInteractiveBrowserCredential.cs

@@ -192,6 +192,16 @@ private void CacheAuthenticationRecord(TokenRequestContext requestContext, Cance
 
     private AuthenticationRecord Authenticate(TokenRequestContext requestContext, CancellationToken cancellationToken)
     {
+        // If a previous attempt already proved the browser flow is unavailable in this
+        // environment (e.g. headless WSL / no GUI), skip straight to device code. Without
+        // this, the retry after RecreateCredentialsWithoutPersistence() would re-enter the
+        // browser path and hang waiting for an OAuth redirect that will never arrive.
+        if (Volatile.Read(ref _isDeviceCodeFallback) == 1)
+        {
+            _logger.LogInformation("Using device code authentication (browser flow previously unavailable)...");
+            return _deviceCodeCredential.Authenticate(requestContext, cancellationToken);
+        }
+
         try
         {
             _logger.LogInformation("Waiting for authentication in the browser...");