Merge pull request #357 from koic/refactor_handle_delete_to_use_helper_methods

Refactor `handle_delete` to use `extract_session_id`

Author: koic

lib/mcp/server/transports/streamable_http_transport.rb

@@ -426,7 +426,7 @@ def handle_delete(request)
             return success_response
           end
 
-          return missing_session_id_response unless (session_id = request.env["HTTP_MCP_SESSION_ID"])
+          return missing_session_id_response unless (session_id = extract_session_id(request))
           return session_not_found_response unless session_exists?(session_id)
 
           protocol_version_error = validate_protocol_version_header(request)