Add IsEnabled guards for received message logging

Guard LogTransportReceivedMessageSensitive calls with IsEnabled(LogLevel.Trace)
checks to avoid unnecessary work when trace logging is disabled.

Co-authored-by: stephentoub <2642209+stephentoub@users.noreply.github.com>

Author: Copilot

src/ModelContextProtocol.Core/Client/SseClientSessionTransport.cs

@@ -198,7 +198,10 @@ private async Task ProcessSseMessage(string data, CancellationToken cancellation
             return;
         }
 
-        LogTransportReceivedMessageSensitive(Name, data);
+        if (_logger.IsEnabled(LogLevel.Trace))
+        {
+            LogTransportReceivedMessageSensitive(Name, data);
+        }
 
         try
         {

src/ModelContextProtocol.Core/Client/StreamClientSessionTransport.cs

@@ -148,7 +148,10 @@ private async Task ReadMessagesAsync(CancellationToken cancellationToken)
                     continue;
                 }
 
-                LogTransportReceivedMessageSensitive(Name, line);
+                if (Logger.IsEnabled(LogLevel.Trace))
+                {
+                    LogTransportReceivedMessageSensitive(Name, line);
+                }
 
                 await ProcessMessageAsync(line, cancellationToken).ConfigureAwait(false);
             }

src/ModelContextProtocol.Core/Client/StreamableHttpClientSessionTransport.cs

@@ -347,7 +347,10 @@ private async Task<SseResponse> ProcessSseResponseAsync(
 
     private async Task<JsonRpcMessageWithId?> ProcessMessageAsync(string data, JsonRpcRequest? relatedRpcRequest, CancellationToken cancellationToken)
     {
-        LogTransportReceivedMessageSensitive(Name, data);
+        if (_logger.IsEnabled(LogLevel.Trace))
+        {
+            LogTransportReceivedMessageSensitive(Name, data);
+        }
 
         try
         {

src/ModelContextProtocol.Core/Server/StreamServerTransport.cs

@@ -112,7 +112,10 @@ private async Task ReadMessagesAsync()
                     continue;
                 }
 
-                LogTransportReceivedMessageSensitive(Name, line);
+                if (Logger.IsEnabled(LogLevel.Trace))
+                {
+                    LogTransportReceivedMessageSensitive(Name, line);
+                }
 
                 try
                 {