Add production NPC pipeline composition

internal/modules/dnd/normalize/npcs/normalizer_test.go

@@ -250,6 +250,21 @@ func TestNormalizeHandlesNilAndCanceledCalls(t *testing.T) {
 	}
 }
 
+func TestNormalizePreservesPresentEmptyAliases(t *testing.T) {
+	result, err := New(Options{}).Normalize(context.Background(), normalizeRequest(dnd.NPCList{NPCs: []dnd.NPC{{
+		Name:        "Hooded Guard",
+		Aliases:     []string{},
+		Description: "A distinguishable sentry.",
+		SourceRefs:  []source.SourceRef{{SourceID: "session", StartUnitID: 1, EndUnitID: 1}},
+	}}}))
+	if err != nil {
+		t.Fatalf("Normalize() error = %v, want nil", err)
+	}
+	if result.Value.NPCs[0].Aliases == nil || len(result.Value.NPCs[0].Aliases) != 0 {
+		t.Fatalf("aliases = %#v, want present empty array", result.Value.NPCs[0].Aliases)
+	}
+}
+
 func normalizeRequest(value dnd.NPCList) contracts.TypedNormalizeRequest[dnd.NPCList] {
 	return contracts.TypedNormalizeRequest[dnd.NPCList]{
 		MergeOutput: contracts.MergeArtifact[dnd.NPCList]{Value: value},