The mesh says what it applied, and the replay has an address it may use

The pipeline was observable from a merge to an artifact and went dark where it touched a machine: a
node's report is control traffic only the control plane reads, so nothing said which version a
machine runs, or that it refused to (novox/hq ADR 0134). The control plane now states both under the
seat it holds — a role's events belong to the role and keep their address when the holder is
replaced — and only when the report is news, because a machine reconciles every minute and a fact per
report would be a fact per minute per machine.

Whether a report is news is the store's answer: it holds the previous one, so the listener returns it
and the server states the fact. That also gives the catch-up replay a subject the controller may
publish: it was published as a module's event from a module called "control-plane", which does not
exist, so the controller's own account refused it and every catalogue that asked what it missed was
answered with nothing.

internal/broker/streams.go

@@ -160,6 +160,17 @@ func Overlaps() []string {
 // ack subject is derived from (nats.go: `$JS.ACK.<stream>.controller.>`).
 const ControllerName = "controller"
 
+// ControllerSeat is the role the control plane holds, and ControllerStates are the facts it states
+// under it (novox/hq ADR 0134).
+//
+// **Written here as well as in `link`, and a test keeps them agreeing.** `link` imports `broker`, so
+// `broker` cannot import `link`; a grant naming a subject the controller never publishes is authority
+// nobody uses, and a controller publishing one the grant omits is refused at the moment it has
+// something to say.
+const ControllerSeat = "mesh-controller"
+
+var ControllerStates = []string{"applied", "refused", "built-before"}
+
 // ControllerFollows are the events the controller reacts to: the catalogue saying a module's
 // current version moved, and a catalogue that has just started saying it may have missed builds.
 //