An agent name was checked for shape and never for meaning, so a name the
system already answers to could be taken. The list is derived, not invented:
operator/manager/root are broker recipients, and forge/reminder/schedule/
system/todo are message senders.
Senders are in it for a reason that is not cosmetic. The harness switches on
the sender name, so an agent called todo would have its messages read as
todo-wakes and one called system as helper events. That is a parse, not a
display quirk.
⚠️ The check is deliberately its own function rather than part of
validate_username, which runs over every user on every write — including
humans this bridge did not create. Folding it in would mean a store already
containing an operator named 'operator' could never be written again: a rule
about what an agent may be NAMED would have become a rule about what the file
may CONTAIN. A test pins that.
This is the static half only. The dynamic half — a name already taken by
another subject — waits on the heal-vs-refuse question open on #3550.
dd1156d45c