Add execution metadata to module specifications

docs/internal/dnd.md

@@ -24,7 +24,11 @@ does not repeat their JSON shapes or schemas.
 The D&D registrar registers the family’s artifact codecs, extractors, typed
 append-order mergers, normalizers, validators, prompt assets, fallback LLM
 profile asset, and default validator chains. Each extractor and normalizer has
-a stable module spec, strict option decoding, and a typed builder.
+a stable module spec, explicit execution class, strict option decoding, and a
+typed builder. Scene chunking, every extractor, and NPC normalization are
+registered as `llm_backed`; the remaining current D&D mergers and normalizers
+are `deterministic`. The metadata is available to catalog inspection and
+resolved-pipeline debug data; it does not yet change profile inheritance.
 Configuration remains the canonical owner of the exact keys and validator
 order.