Run D&D spell lanes through typed artifacts

internal/framework/pipeline/artifact_codec_registry.go

@@ -63,10 +63,12 @@ type ArtifactCodecRegistry struct {
 }
 
 type artifactCodecEntry struct {
-	spec      ArtifactCodecSpec
-	valueType reflect.Type
-	encode    func(any) ([]byte, error)
-	decode    func([]byte) (any, error)
+	spec            ArtifactCodecSpec
+	valueType       reflect.Type
+	encode          func(any) ([]byte, error)
+	encodeCandidate func(any) ([]byte, error)
+	metadata        func(any) map[string]any
+	decode          func([]byte) (any, error)
 }
 
 func NewArtifactCodecRegistry() *ArtifactCodecRegistry {
@@ -118,6 +120,29 @@ func RegisterArtifactCodec[T any](registry *ArtifactCodecRegistry, codec contrac
 			return decoded, nil
 		},
 	}
+	entry.encodeCandidate = entry.encode
+	if candidate, ok := any(codec).(interface{ EncodeCandidate(T) ([]byte, error) }); ok {
+		entry.encodeCandidate = func(value any) ([]byte, error) {
+			typed, err := exactTypedValue[T]("encode candidate artifact", value)
+			if err != nil {
+				return nil, err
+			}
+			content, err := candidate.EncodeCandidate(typed)
+			if err != nil {
+				return nil, &ArtifactCodecOperationError{Operation: "encode", Kind: spec.Kind, Err: err}
+			}
+			return append([]byte(nil), content...), nil
+		}
+	}
+	if provider, ok := any(codec).(interface{ Metadata(T) map[string]any }); ok {
+		entry.metadata = func(value any) map[string]any {
+			typed, err := exactTypedValue[T]("artifact metadata", value)
+			if err != nil {
+				return nil
+			}
+			return cloneMetadata(provider.Metadata(typed))
+		}
+	}
 	if registry.entries == nil {
 		registry.entries = make(map[contracts.ArtifactKind]artifactCodecEntry)
 	}