The rollout moves every node at once, so there is nothing to inspect afterwards and no
half to roll back — either the mesh was ready or it was not. That makes the readiness
question the valuable half: it costs nothing, it can be asked of a mesh that is serving as
many times as you like, and every answer is a thing somebody can go and fix.
It reads from records and dials once. Is a bus answering, does a machine hold the seat, has
that machine been sent the composed user list, does every machine have a credential for the
new bus, does every module that speaks. Each missing thing names its own next step, because
"not ready" that cannot be acted on is not an answer — and this is read at the point where
the next step is irreversible.
**A machine with no credential is the one that must stop it.** It keeps running and cannot
come back, and afterwards there is no bus to tell it anything over, so the remedy has to
happen first. The message says so.
A module that never reaches the bus is not counted as missing a credential. A third of the
catalogue never speaks, and listing those would bury the ones that matter.
`rollout --confirm` refuses and says why: the move is not being written before its check has
been run against a real mesh. And the plan it prints says the old broker stays — it remains
an ordinary provider of `amqp` for whatever else uses it, which on this installation is a
whole automation layer that has nothing to do with the mesh. This move is not its retirement,
and that is why it is survivable: what breaks if it goes wrong is the mesh's ability to
change things, not the services its modules serve.
