One build machine built everything, in a queue of one, because the seat was mesh-scoped and a
mesh seat has one holder. ADR 0190 makes building a node role: node-build-agent, held on every
machine that builds, with the work asked of the role and taken by whichever holder is idle. The
work subject of a node-scoped seat carries no node — that token is for a seat's tools, asked of
one machine (design 33 §4) — so holders on several machines read one queue; a test now says so.
The retired mesh-build-machine row stays while the builder module's registered manifest claims
it: a claim to a seat the mesh no longer defines is refused, and the machine holding it would be
unresolvable until build-agent replaces it. Removed once no manifest claims it.
The installer's genesis template (in the host's repository) still grants the controller the old
seat's subjects; its test here says so until that template names node-build-agent.