C2b: a seat verb's no responders is a transport fault when the assigner names a holder of the seat; a seat nothing holds fails at once (ADR 0664 §1, issue 1748)

Claude-Session: https://claude.ai/code/session_01JG73KEq4zoDfM9WtYpcQgZ

modules/mesh-build-image/cmd/mesh-build-image/compose_test.go

@@ -24,7 +24,7 @@ func TestTheModuleInvokesTheImageSeatAndHoldsNoRegistry(t *testing.T) {
 		t.Fatal(err)
 	}
 	if want := []string{"seat:container-image-registry.publish", "seat:container-image-registry.publish-part",
-		"seat:container-image-registry.mirror"}; !slices.Equal(m.Invokes, want) {
+		"seat:container-image-registry.mirror", "seat:mesh-module-assigner.assignments"}; !slices.Equal(m.Invokes, want) {
 		t.Errorf("invokes = %v, want %v", m.Invokes, want)
 	}
 	// The builder's version.numbered for the late publish (ADR 0617 §1), and the seat's outcomes a copy waits on.

modules/mesh-build-image/cmd/mesh-build-image/publish.go

@@ -136,7 +136,7 @@ func (m *Module) publish(ctx context.Context, workspace, module, local string, r
 		Transfer: buildstep.TransferName(name, q, img.Digest)}
 	sent, err := buildstep.PublishFiles(ctx, m.call(), buildstep.ImageSeat, in, img.Files)
 	if err != nil {
-		return nil, fmt.Errorf("%s%s: %v", builds.NotStored, res.Artifact, err)
+		return nil, fmt.Errorf("%s%s: %w", builds.NotStored, res.Artifact, err)
 	}
 	m.say("published %s on %s: %d of its %d parts sent, the rest held", name, buildstep.ImageSeat, len(sent.Parts), len(img.Files))
 	res.Digest, res.Pushed = img.Digest, true