Add ability for client to resume session (#1029)

src/ModelContextProtocol.Core/Client/AutoDetectingClientSessionTransport.cs

@@ -93,6 +93,11 @@ internal sealed partial class AutoDetectingClientSessionTransport : ITransport
 
     private async Task InitializeSseTransportAsync(JsonRpcMessage message, CancellationToken cancellationToken)
     {
+        if (_options.KnownSessionId is not null)
+        {
+            throw new InvalidOperationException("Streamable HTTP transport is required to resume an existing session.");
+        }
+
         var sseTransport = new SseClientSessionTransport(_name, _options, _httpClient, _messageChannel, _loggerFactory);
 
         try