An address is read from the node's settings where it is used, never recorded with a port

Three readers did not follow a moved foundation port (novox/hq 04-ISSUES/102),
and each took the control-node down in its own way: the control plane's own
store and broker connections, sealed at genesis with the port inside; and every
build the mesh ever recorded, kept as `<registry>:<port>/<module>/<artifact>@…`.

The control plane cannot open its own sealed connections to move a port, and it
cannot bind the store as a consumer would — a binding mints a credential. So its
settings get a third twin, `NAME_PORT`, read on top of the sealed value by the
store, the broker, the management API and the bus connection, and filled into
its container by a placeholder that names a seat, `${seat:mesh-store:5432}`,
from the node's given or mesh-assigned ports — never the manifest's number, and
empty when the mesh has nothing to add, so what genesis wrote stands. A value
that is still a placeholder is nothing said, aloud: the manifest naming it lands
in the next commit, once every control plane that composes it knows it.

A build is now recorded by digest and path — `artifact-store://<module>/<artifact>@…`
— and the store's address is composed in where a reference is used: the
declaration, the trust file, the bases a build is handed, a replay to the
catalogue. Over the network as `<node>.internal:<port>`; on the store's own node
before any network exists — every genesis push before its "network" step — by
loopback. A reference recorded before this, with an address, is re-routed the
same way when the mesh built it. The trust file and every provider's address
come from one derivation: the node's given port, over the mesh's assignment,
over the manifest's number.

novox/hq 04-ISSUES/102

internal/link/serve.go

@@ -146,8 +146,12 @@ func (s *Server) Answers(r Replayer) error {
 }
 
 // Connect opens the control plane's own connection to the broker.
+//
+// On the port MESH_BROKER_AMQP_PORT names when the node's settings moved the broker (novox/hq
+// 04-ISSUES/102) — the URL is genesis's, sealed, and its port is the one thing in it the node may
+// have moved since.
 func Connect(enroller Enroller, listener Listener) (*Server, error) {
-	url, err := envfile.Value(AMQPVar)
+	url, err := envfile.Placed(AMQPVar)
 	if err != nil {
 		return nil, err
 	}