Migrate NPC registry durable contract

internal/modules/dnd/npcs/identity/identity.go

@@ -5,6 +5,7 @@ package identity
 import (
 	"crypto/sha256"
 	"encoding/hex"
+	"encoding/json"
 	"fmt"
 	"strings"
 
@@ -17,7 +18,7 @@ import (
 const (
 	// Policy identifies the complete identity comparison and ID derivation
 	// policy. A future semantic change must use a new value.
-	Policy = "dnd.npcs.identity.v1"
+	Policy = "dnd.npc_registry.identity.v1"
 	// IdentityPolicy is an explicit alias for callers recording policy
 	// fingerprints.
 	IdentityPolicy = Policy
@@ -72,7 +73,11 @@ func DeriveID(name string) string {
 	if key == "" {
 		return ""
 	}
-	digest := sha256.Sum256([]byte(key))
+	identity, err := json.Marshal([]string{Policy, key})
+	if err != nil {
+		return ""
+	}
+	digest := sha256.Sum256(identity)
 	return idPrefix + hex.EncodeToString(digest[:])
 }
 
@@ -98,7 +103,7 @@ func ValidID(value string) bool { return IsValidID(value) }
 
 // ValidateRegistry checks all identity invariants without changing the input.
 // It accepts the NPC slice used by typed pipeline artifacts. Use ValidateList
-// when the enclosing NPCList is more convenient at the call site.
+// when the enclosing NPCRegistry is more convenient at the call site.
 func ValidateRegistry(npcs []dnd.NPC) []Issue {
 	issues := make([]Issue, 0)
 	canonicalOwners := make(map[string][]int)
@@ -136,7 +141,7 @@ func ValidateRegistry(npcs []dnd.NPC) []Issue {
 }
 
 // ValidateList validates the identity members of list.
-func ValidateList(list dnd.NPCList) []Issue { return ValidateRegistry(list.NPCs) }
+func ValidateList(list dnd.NPCRegistry) []Issue { return ValidateRegistry(list.NPCs) }
 
 // Error makes an issue useful in simple callers while preserving its
 // structured fields for aggregate diagnostics.

internal/modules/dnd/npcs/identity/identity_test.go

@@ -1,6 +1,7 @@
 package identity
 
 import (
+	"reflect"
 	"strings"
 	"sync"
 	"testing"
@@ -40,9 +41,16 @@ func TestNormalizeDisplayOnlyChangesWhitespace(t *testing.T) {
 
 func TestDeriveIDAndIDSyntax(t *testing.T) {
 	got := DeriveID("  Mira\u2003Thorn ")
+	const want = "npc:sha256:35ba5f679aee69e07ae3bd65c44278f29539d5dc9bb5225db1c0060555b23221"
+	if Policy != "dnd.npc_registry.identity.v1" || IdentityPolicy != Policy {
+		t.Fatalf("identity policy = %q/%q", Policy, IdentityPolicy)
+	}
 	if len(got) != len("npc:sha256:")+64 || !strings.HasPrefix(got, "npc:sha256:") || !IsValidID(got) {
 		t.Fatalf("DeriveID() = %q, want exact NPC ID syntax", got)
 	}
+	if got != want {
+		t.Fatalf("DeriveID() = %q, want SHA-256 of compact JSON [policy, comparison_name]", got)
+	}
 	if got != DeriveID("Mira Thorn") || got != IDFor("Mira Thorn") {
 		t.Fatal("DeriveID() is not deterministic across equivalent names")
 	}
@@ -80,7 +88,11 @@ func TestValidateRegistryReportsIdentityCollisionCategories(t *testing.T) {
 		{ID: validID, Name: "Mira Thorn"},
 		{ID: validID, Name: "Mira Thorn"},
 	}
+	before := append([]dnd.NPC(nil), npcs...)
 	issues := ValidateRegistry(npcs)
+	if !reflect.DeepEqual(npcs, before) {
+		t.Fatal("ValidateRegistry() mutated its input")
+	}
 	want := map[IssueCode]bool{
 		IssueDuplicateCanonical: false,
 		IssueDuplicateID:        false,

internal/modules/dnd/npcs/registry/registry.go

@@ -27,7 +27,7 @@ const (
 // grounding. All accessors return defensive copies.
 type Registry struct {
 	bound            bool
-	list             dnd.NPCList
+	list             dnd.NPCRegistry
 	canonical        []byte
 	digest           string
 	projectionDigest string
@@ -105,7 +105,7 @@ func emptyRegistry() *Registry {
 	content := []byte(emptyPrompt)
 	projectionDigest := semanticDigest(content)
 	return &Registry{
-		list:             dnd.NPCList{NPCs: []dnd.NPC{}},
+		list:             dnd.NPCRegistry{NPCs: []dnd.NPC{}},
 		canonical:        append([]byte(nil), content...),
 		projectionDigest: projectionDigest,
 		promptInput:      contracts.NewLLMInputMaterial(ReferenceSlot, npccodec.MediaType, content, projectionDigest, ""),
@@ -127,7 +127,7 @@ func loadRegistry(referenceContent []byte) (*Registry, error) {
 		return nil, fmt.Errorf("encode canonical NPC registry: approved NPC value could not be encoded")
 	}
 
-	list := cloneNPCList(value)
+	list := cloneNPCRegistry(value)
 	lookupByKey := make(map[string]int, len(list.NPCs))
 	for index, npc := range list.NPCs {
 		lookupByKey[identity.ComparisonKey(npc.Name)] = index
@@ -161,11 +161,11 @@ func (r *Registry) NPCs() []dnd.NPC {
 }
 
 // List returns a defensive copy of the validated NPC list.
-func (r *Registry) List() dnd.NPCList {
+func (r *Registry) List() dnd.NPCRegistry {
 	if r == nil {
-		return dnd.NPCList{}
+		return dnd.NPCRegistry{}
 	}
-	return cloneNPCList(r.list)
+	return cloneNPCRegistry(r.list)
 }
 
 // CanonicalBytes returns a defensive copy of the canonical durable JSON.
@@ -233,12 +233,12 @@ type projectedNPC struct {
 	Name string `json:"name"`
 }
 
-type projectedNPCList struct {
+type projectedNPCRegistry struct {
 	NPCs []projectedNPC `json:"npcs"`
 }
 
-func nameProjection(list dnd.NPCList) ([]byte, error) {
-	projection := projectedNPCList{NPCs: make([]projectedNPC, len(list.NPCs))}
+func nameProjection(list dnd.NPCRegistry) ([]byte, error) {
+	projection := projectedNPCRegistry{NPCs: make([]projectedNPC, len(list.NPCs))}
 	for index, npc := range list.NPCs {
 		projection.NPCs[index] = projectedNPC{Name: npc.Name}
 	}
@@ -254,8 +254,8 @@ func formatIdentityIssues(issues []identity.Issue) string {
 	return diagnostics.Aggregate("validate NPC registry identity", parts)
 }
 
-func cloneNPCList(value dnd.NPCList) dnd.NPCList {
-	return dnd.NPCList{NPCs: cloneNPCs(value.NPCs)}
+func cloneNPCRegistry(value dnd.NPCRegistry) dnd.NPCRegistry {
+	return dnd.NPCRegistry{NPCs: cloneNPCs(value.NPCs)}
 }
 
 func cloneNPCs(values []dnd.NPC) []dnd.NPC {

internal/modules/dnd/npcs/registry/registry_test.go

@@ -164,14 +164,14 @@ func TestResolverHandlesConstructionAndOperationReferences(t *testing.T) {
 	}
 }
 
-func registryFixture() dnd.NPCList {
-	return dnd.NPCList{NPCs: []dnd.NPC{
+func registryFixture() dnd.NPCRegistry {
+	return dnd.NPCRegistry{NPCs: []dnd.NPC{
 		{ID: identity.DeriveID("Mira Thorn"), Name: "Mira Thorn", SourceRefs: []source.SourceRef{{SourceID: "session-alpha", StartUnitID: 1, EndUnitID: 2}}},
 		{ID: identity.DeriveID("Captain Vale"), Name: "Captain Vale", SourceRefs: []source.SourceRef{{SourceID: "session-alpha", StartUnitID: 3, EndUnitID: 3}}},
 	}}
 }
 
-func resolveList(t *testing.T, list dnd.NPCList) *Registry {
+func resolveList(t *testing.T, list dnd.NPCRegistry) *Registry {
 	t.Helper()
 	registry, err := Resolve(listReferenceSet(t, list))
 	if err != nil {
@@ -180,7 +180,7 @@ func resolveList(t *testing.T, list dnd.NPCList) *Registry {
 	return registry
 }
 
-func listReferenceSet(t *testing.T, list dnd.NPCList) contracts.ReferenceSet {
+func listReferenceSet(t *testing.T, list dnd.NPCRegistry) contracts.ReferenceSet {
 	t.Helper()
 	content, err := npccodec.New().Encode(list)
 	if err != nil {