mesh-delivery-sdk: the runner's stale-step part moves to package buildrun, so buildstep (layouts, keys, codecs) and the builder's published builds package reach no bus; a test each refuses it (B6e finding 5; ADR 0634 §1; issue 1966)

Claude-Session: https://claude.ai/code/session_01NcbgfFSnn24M3GcqttoU7i

modules/mesh-delivery-builder/builds/busfree_test.go

@@ -0,0 +1,21 @@
+package builds
+
+import (
+	"os/exec"
+	"strings"
+	"testing"
+)
+
+// The builder's published value is read by modules that never touch the bus (mesh-host's composer tool): nothing it
+// imports reaches the bus library.
+func TestThePackageReachesNoBus(t *testing.T) {
+	out, err := exec.Command("go", "list", "-deps", ".").Output()
+	if err != nil {
+		t.Fatalf("go list: %v", err)
+	}
+	for _, p := range strings.Fields(string(out)) {
+		if strings.HasPrefix(p, "github.com/nats-io/") {
+			t.Errorf("builds depends on %s", p)
+		}
+	}
+}