delivery: a composition carries no signature, since the node applies only what it composes itself (ADR 0593 §6)

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

go/delivery/compose_candidate_test.go

@@ -101,6 +101,13 @@ func TestComposeCandidateAndComposedPlanRoundTripAndRefuse(t *testing.T) {
 	if SameComposed(planned, Composed{Node: "ace", Module: "netcheck", FP: fp, Resources: []json.RawMessage{}}) {
 		t.Error("a plan change is not a new composition value")
 	}
+	signed := strings.Replace(string(raw), `"resources"`, `"signature":{"signer":"x","sig":"y"},"resources"`, 1)
+	if c, err := DecodeComposed([]byte(signed)); err != nil || c.Node != "ace" {
+		t.Fatalf("a composition the ended controller signed does not decode: %v", err)
+	}
+	if strings.Contains(string(raw), "signature") {
+		t.Error("a composition is written with a signature")
+	}
 	refused := Composed{Node: "ace", Module: "netcheck", FP: fp, Refused: "the setting domain has no value"}
 	if raw, err = EncodeComposed(refused); err != nil {
 		t.Fatal(err)