Add reference contracts to extractor metadata

internal/framework/contracts/contracts.go

@@ -74,10 +74,49 @@ type Chunker interface {
 	Chunk(ctx context.Context, req ChunkRequest) (ChunkResult, error)
 }
 
+const (
+	ReferenceBindingSourceConfig = "config"
+	ReferenceBindingSourceCLI    = "cli"
+)
+
+type ReferenceSlot struct {
+	Name               string   `json:"name"`
+	Description        string   `json:"description,omitempty"`
+	Required           bool     `json:"required,omitempty"`
+	AcceptedMediaTypes []string `json:"accepted_media_types,omitempty"`
+	Multiple           bool     `json:"multiple,omitempty"`
+	MaxBytes           int64    `json:"max_bytes,omitempty"`
+}
+
+type ReferenceOrigin struct {
+	Type string `json:"type"`
+	URI  string `json:"uri,omitempty"`
+}
+
+type ReferenceItem struct {
+	SlotName      string          `json:"slot_name"`
+	MediaType     string          `json:"media_type,omitempty"`
+	Content       []byte          `json:"-"`
+	Digest        string          `json:"digest,omitempty"`
+	Origin        ReferenceOrigin `json:"origin"`
+	SizeBytes     int64           `json:"size_bytes,omitempty"`
+	BindingSource string          `json:"binding_source,omitempty"`
+}
+
+type ResolvedReferenceSlot struct {
+	Slot  ReferenceSlot   `json:"slot"`
+	Items []ReferenceItem `json:"items,omitempty"`
+}
+
+type ReferenceSet struct {
+	Slots map[string]ResolvedReferenceSlot `json:"slots,omitempty"`
+}
+
 type ExtractionRequest struct {
 	Source         *source.SourceDocument `json:"-"`
 	Chunk          *SourceChunk           `json:"chunk,omitempty"`
 	AmbientContext map[string]any         `json:"ambient_context,omitempty"`
+	References     ReferenceSet           `json:"references,omitempty"`
 	LLMClient      StructuredLLMClient    `json:"-"`
 	LLMProfile     string                 `json:"llm_profile,omitempty"`
 	Options        map[string]any         `json:"options,omitempty"`
@@ -93,6 +132,7 @@ type Extractor interface {
 	Key() string
 	ArtifactType() string
 	SchemaVersion() string
+	ReferenceSlots() []ReferenceSlot
 	Validators() []Validator
 	Extract(ctx context.Context, req ExtractionRequest) (ExtractionResult, error)
 }