- notify_parent: adds Reply-To set to the first CC (admin) address so
parent replies to the completion confirmation reach the admin rather
than re-entering the agent pipeline
- notify_admin / notify_registration_update: Reply-To = parent email
was already wired through _send(); confirmed with new tests
- Mid-registration send_reply emails carry no Reply-To (verified by test)
- 5 new tests across TestNotifyParentReplyTo and TestNotifyAdminReplyTo;
1 new test in TestSendReplyNoAdminReplyTo (174 passing, 0 failing)
https://claude.ai/code/session_014NynTjALA5TeP85mbr5ZA8