Address review feedback

Author: duboff

lib/mcp/server.rb

@@ -314,9 +314,9 @@ def server_info
     end
 
     def init(params)
-      client_version = params&.dig(:protocolVersion) || params&.dig("protocolVersion")
-      negotiated_version = if client_version && Configuration::SUPPORTED_STABLE_PROTOCOL_VERSIONS.include?(client_version)
-        client_version
+      protocol_version = params[:protocolVersion] if params
+      negotiated_version = if protocol_version && Configuration::SUPPORTED_STABLE_PROTOCOL_VERSIONS.include?(protocol_version)
+        protocol_version
       else
         configuration.protocol_version
       end