Add NPC registry grounding for spell extraction

docs/integrations/dnd-spell-artifacts.md

@@ -94,6 +94,22 @@ Reference slot keys and accepted file types are defined in
 supporting disambiguation material, not source evidence, and are not
 addressable through `source_refs`.
 
+## Optional NPC Grounding
+
+The `dnd/spells` extractor accepts an optional `npcs` reference containing one
+normalized NPC artifact as `application/json`, up to 1 MiB. Preparation uses
+the approved NPC codec and identity policy to validate the file, re-encodes
+canonical durable JSON, and supplies that JSON as a spell-owned prompt input.
+It helps the model prefer canonical caster names and recognize aliases; it
+does not establish that a spell was cast.
+
+NPC source references may identify the run that produced the registry or any
+other session. They remain registry provenance and are never copied into a
+spell cast's `source_refs`; every spell evidence range must still identify the
+current transcript. When the slot is absent, the prompt receives exactly
+`{"npcs":[]}` and the run has no NPC reference provenance or NPC checkpoint
+fingerprint.
+
 ## Normalization Behavior
 
 When the `dnd/spells` normalizer is selected, each recognized spell name is
@@ -153,7 +169,9 @@ manifest metadata:
       "response_schema_sha256": "sha256:...",
       "catalog_base_id": "dnd-5e-2014-srd-spells",
       "catalog_digest": "sha256:...",
-      "catalog_overlay_ids": ["campaign.example"]
+      "catalog_overlay_ids": ["campaign.example"],
+      "npc_registry_digest": "sha256:...",
+      "npc_count": 3
     },
     "normalizer": {
       "catalog_base_id": "dnd-5e-2014-srd-spells",
@@ -172,8 +190,15 @@ identity fields when that module is selected. Overlay origin, media type, byte
 size, and raw digest are recorded separately in the manifest's reference
 provenance; see the [JSON output contract](json-output.md#manifestjson).
 
+The `npc_registry_digest` and `npc_count` fields in the example are present only
+when the optional NPC registry is bound. They contain no NPC names, aliases,
+source references, paths, or raw bytes.
+
 The extractor's prompt hash, private response-schema hash, and effective catalog
 digest also contribute independently scoped semantic checkpoint fingerprints.
 Changing any of those prepared contracts intentionally produces a cold
 checkpoint miss. Fingerprints contain only digests, never prompt, schema,
-catalog, or reference content.
+catalog, or reference content. When an NPC registry is bound, its semantic
+digest contributes an additional local `npc_registry` fingerprint; the
+manifest metadata contains only that digest and `npc_count`. Raw NPC file
+provenance remains independently recorded in the manifest's `references` list.