The controller now composes a publish grant for its lease bucket
($KV.mesh-controller_lease.>), which it must write before it acts, and for
the seat event secret-replaced (hq ADR 0228, mesh-controller #82); and it no
longer publishes mesh.control.>: a machine's report has one writer, its
node-engine, and the writers table refuses a second at composition. The
installer's first user list must say what the controller derives, or a new
mesh's first controller is refused its lease and serves without one.