Introduce typed D&D spell artifacts

docs/integrations/dnd-spell-artifacts.md

@@ -6,6 +6,7 @@ extractor. Selectable extractor keys are cataloged in
 
 ## Identity
 
+- Artifact kind: `dnd/spell-list`
 - Prompt ID: `dnd.spells`
 - Response schema key: `dnd_spells`
 - Response schema ID: `notarius.dnd.spells`
@@ -13,6 +14,12 @@ extractor. Selectable extractor keys are cataloged in
 - Response schema version: `v1`
 - Media type: `application/json`
 
+The durable JSON Schema is owned by the D&D spell artifact codec. The
+extractor's private LLM response schema is a separate transport contract: its
+source-reference objects omit `source_id`, which the extractor assigns while
+mapping the response to the canonical artifact. The LLM DTO and transport
+schema are not part of this durable contract.
+
 The output contains canonical spell casts derived from transcript evidence.
 Source IDs are assigned from the input identity; source-unit ranges identify
 the evidence location.