Errors and Network Error Bundle
================================

Never put the intended recipient payload in an error object.

* **ct_sender** -- failure status encrypted so **only the sender** can read it.
* **ct_system** -- bounce report encrypted to the **system public key** for
  logging/recovery (lookup_id, error_code, dest_class, respond flag).
* **Dead letter** -- ``verae.sm.dead`` with the same bundle.
* **Central log** -- ``verae.sm.log.summary``: codes only.

The sender identifies the original message with ``lookup_id``, not by
decrypting what they sent.