;;; -*- scheme -*-
;;; external_delivery_reply — repro for task #128 (ActiveHolder
;;; `_20._61`): a nondet-reply requires-call in a reply-gated chain
;;; INSIDE an external out-event delivery handler. Fixed by
;;; step_frontier::try_external_delivery (delivery handlers now get
;;; fork-at-reply EXTERNAL choice). Companion to
;;; external_spont_reply_split (provides-handler class). Passing guard.
