The swarm queue's rendered settings never named max_payload, so it ran
on nats-server's upstream default of 1 MiB. That default is about to
be too small: the broker is going to carry agent terminal rows
(whole TermMsg bodies) published as complete messages rather than
split, and a publish over the limit does not truncate — the server
answers -ERR 'Maximum Payload Violation' and closes the connection,
dropping the row.
Set max_payload = 8388608 explicitly in the settings merge, with a
comment on what it bounds and what bounds it (max_pending, which
nats-server refuses to start past). Add a module-eval case that reads
the rendered container config so a future edit that drops or shadows
the key fails eval instead of surfacing as a dropped row in
production.
Refs #3805
09d502ea34