The build role is the node-scoped seat node-build-agent, and its work is shared by every holder (hq ADR 0190)

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.

internal/broker/nats.go

@@ -110,10 +110,10 @@ type Principal struct {
 	PasswordHash string
 }
 
-// meshSeatsTheControllerUses are the roles the mesh's own flows submit work to. Named rather than
+// seatsTheControllerAsks are the roles the mesh's own flows submit work to. Named rather than
 // derived from the seat set: the controller is not a module and declares no `uses`, so its side of a
 // seat has to be stated, and a list is what makes "which roles does the mesh itself talk to" answerable.
-var meshSeatsTheControllerUses = []string{"mesh-build-machine"}
+var seatsTheControllerAsks = []string{"node-build-agent"}
 
 // enrolmentPrefix is the space every enrolling node's user and inbox live under, so the one place the
 // controller may answer an enrolment is derived from the same constant the user is named from.
@@ -208,7 +208,9 @@ func PermissionsFor(p Principal) (Permissions, error) {
 		// Work the mesh's own flows submit to a role, and the outcomes they wait on (ADR 0121). A
 		// build is the one today: the controller asks, and reads the answer from the seat's event
 		// like the catalogue does — which is why no holder needs to publish into anybody's inbox.
-		for _, seat := range meshSeatsTheControllerUses {
+		// A node-scoped seat's work subject carries no node (novox/hq ADR 0190): the ask goes to
+		// the role, and whichever machine holding it is idle takes it.
+		for _, seat := range seatsTheControllerAsks {
 			pub = append(pub, "mesh.seat."+seat+".accept.>")
 		}
 		// **And what the mesh says it did** (novox/hq ADR 0134). The control plane states its own