Finish the references implementation for the extraction module and update roadmap documentation

docs/internal/modules.md

@@ -25,7 +25,10 @@ through both `ReferenceSlots()` and `ModuleSpec().ReferenceSlots`. The runtime
 slot list and registry metadata should match so config validation can inspect
 slots without constructing extractor instances. A slot declaration names the
 slot, whether it is required, accepted media types, whether multiple items are
-allowed, and any byte limit.
+allowed, and any byte limit. Empty `AcceptedMediaTypes` means any inferred
+media type is accepted, though the file must still be UTF-8 text. When a slot
+declares accepted media types, Notarius compares the canonical base media type
+inferred from the file extension, case-insensitively and without parameters.
 
 Reference content is delivered only to the lane extractor through
 `contracts.ExtractionRequest.References`. It is not source evidence and must not
@@ -140,9 +143,10 @@ metadata under `artifact_lanes[].metadata.extractor`. Durable artifact payload
 details belong in the
 [D&D spell artifact contract](../integrations/dnd-spell-artifacts.md).
 
-The extractor declares optional `roster` and `glossary` reference slots accepting
-UTF-8 text. Its prompt frames references as supporting disambiguation material
-only; spell-cast artifacts must still be grounded in the source transcript.
+The extractor declares optional `roster` and `glossary` reference slots
+accepting UTF-8 text without narrowing accepted media types. Its prompt frames
+references as supporting disambiguation material only; spell-cast artifacts must
+still be grounded in the source transcript.
 
 ## D&D Spell Validators