Two-layer gating per CLAUDE.md:
- registration-time: emailgen added to MASTER_ONLY_GROUPS so agents
don't see the sub-app in 'decnet --help' at all.
- body-guard: _require_master_mode('emailgen ...') at the top of every
sub-command body so a direct callable import (third-party tooling)
still bails on agent hosts.
Matches the convention used for 'swarm', 'topology', 'geoip'. SWARM
agents push their generated mail through the master's emailgen worker
(or none at all); cross-agent emailgen federation stays out of scope.
anti
73692b52f0