Per mara on the PR: the guide someone follows on a fresh deploy is a
different page from the one they read while debugging, and only the
second existed.
Also fixes a contradiction the request surfaced: setup.md and
swarm/sso.md have told every operator to create '--group admins' since
the bootstrap step existed, while the new rule required 'operators'.
This is the first rule that CONSUMES a group name, so it takes the one
the guide already creates - inventing a second would have meant every
account made by following the guide silently failing the check it was
supposed to pass, and for mara specifically a migration step that now
may not be needed at all.
setup.md's step 3 says why --group is not decoration; the new step 4
says what decides whether the page opens (the group, and the name
resolving) rather than listing a command, because there is nothing to
run. Steps renumbered, including the matrix block's internal 4a-4e.
New docs/swarm/ui.md (split-page shape, per the docs rule), linked from
the swarm README and added to the gateway's vhost map.
Leads with the step that separates 'protected' from 'locked out':
swarmctl user add <you> --group operators. auth_request asks whether
there is a session; the access_control rule is what makes it mean
operator, and an account created before the rule existed has no groups.
Also records the four wiring sites a swarm service name needs, with the
certificate one called out - serviceDomains is both the sub-CA's
nameConstraints set and the leaf's SANs, and the apex is a sibling of
the other three rather than a parent, so nothing issues for it
implicitly.
