The installer could not raise a first node: the old bundle's control plane had no
MESH_BUS_NATS and crash-looped, and the NATS bundle was refused because rootsecrets
only knew the previous broker's guest:guest@ template.
One bundle now, the NATS one. rootsecrets makes the controller's bus account and puts
it in both placeholders (the address and the bcrypt hash in the carried user list),
kept with its hash so a re-run writes the same bundle. Preflight refuses a template
naming no bus connection it knows, naming the placeholder, instead of waiting out the
verify step. The broker step adopts the bus as the nats module and refuses, by name,
a catalogue without it or a server that is not the foundation's container.
