Enhance HTTP and MCP session logging (modelcontextprotocol#608)

Author: theojiang25

src/ModelContextProtocol.Core/McpSession.cs

@@ -95,6 +95,7 @@ public McpSession(
         _requestHandlers = requestHandlers;
         _notificationHandlers = notificationHandlers;
         _logger = logger ?? NullLogger.Instance;
+        LogSessionCreated(EndpointName, _sessionId, _transportKind);
     }
 
     /// <summary>
@@ -701,6 +702,7 @@ public void Dispose()
         }
 
         _pendingRequests.Clear();
+        LogSessionDisposed(EndpointName, _sessionId, _transportKind);
     }
 
 #if !NET
@@ -783,4 +785,10 @@ private static TimeSpan GetElapsed(long startingTimestamp) =>
 
     [LoggerMessage(Level = LogLevel.Trace, Message = "{EndpointName} sending message. Message: '{Message}'.")]
     private partial void LogSendingMessageSensitive(string endpointName, string message);
+
+    [LoggerMessage(Level = LogLevel.Trace, Message = "{EndpointName} session {SessionId} created with transport {TransportKind}")]
+    private partial void LogSessionCreated(string endpointName, string sessionId, string transportKind);
+
+    [LoggerMessage(Level = LogLevel.Trace, Message = "{EndpointName} session {SessionId} disposed with transport {TransportKind}")]
+    private partial void LogSessionDisposed(string endpointName, string sessionId, string transportKind);
 }