Repair egregious (?!?!) bug where an entity would hash (?) or compare (?) different to itself when used as part of a key in a hash-table in a skeleton

syndicate/entity-ref.rkt

@@ -19,7 +19,6 @@
 (require "engine.rkt")
 
 (struct entity (id name assert retract message sync data)
-  #:transparent
   #:methods gen:custom-write
   [(define (write-proc e port mode)
      (fprintf port "#<entity:~a:~a>" (entity-id e) (entity-name e)))])