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.