Prepare canonical party and derived players inputs

docs/internal/artifacts.md

@@ -39,7 +39,10 @@ ID.
 Prepared stable source IDs are `narratio.input.players`,
 `narratio.input.party`, `narratio.input.glossary`, and
 `narratio.input.spell_catalog`. Artifact policy owns their canonical manifest
-kind and prepared filename vocabulary.
+kind and prepared filename vocabulary. Canonical party mode preserves the
+party source bytes in the party record and supplies the players record from the
+deterministic `derived_from_party` projection; both remain ordinary prepared
+source IDs for consumers.
 
 ## Runtime Catalog