builder: the held fake in its integration tests answers on the artifact sweep's seat, which the builder now asks instead of the controller

Claude-Session: https://claude.ai/code/session_01NcbgfJ9Gum47zkFKWRaovL

modules/mesh-delivery-builder/cmd/mesh-delivery-builder/gone_integration_test.go

@@ -12,6 +12,7 @@ import (
 	"github.com/nats-io/nats.go"
 	"github.com/nats-io/nats.go/jetstream"
 
+	"git.novox.be/novox/mesh-sdk/go/catalogue"
 	"git.novox.be/novox/mesh-sdk/go/delivery"
 )
 
@@ -19,7 +20,7 @@ import (
 // (novox/hq issue 1937): on 2026-10-24 the store's 03:30 collection deleted the bare blobs of three done keys the
 // controller had never taken in, and the builder kept them done.
 
-// heldVerb answers the controller seat's verb held on the bus, as the serving controller does: {result: {output, ok,
+// heldVerb answers the seat mesh-artifact-sweep's verb held on the bus, as its holder does: {result: {output, ok,
 // answer}}; a reference is gone while gone says so.
 type heldVerb struct {
 	mu    sync.Mutex
@@ -29,7 +30,7 @@ type heldVerb struct {
 
 func (h *heldVerb) serve(t *testing.T, b *bed) {
 	t.Helper()
-	sub, err := b.js.Conn().Subscribe("mesh.seat.mesh-controller.call.held.>", func(m *nats.Msg) {
+	sub, err := b.js.Conn().Subscribe("mesh.seat."+catalogue.ArtifactSweepSeat+".call.held.>", func(m *nats.Msg) {
 		var args struct {
 			References []string `json:"references"`
 		}