Add public artifact reader support

types.go

@@ -126,6 +126,14 @@ type Artifact struct {
 	Hash        string
 }
 
+// ArtifactReader resolves a prompt input reference into its content.
+//
+// Readers are responsible for supplying artifact metadata. The engine assigns
+// an input-map name only when the returned artifact name is empty.
+type ArtifactReader interface {
+	Read(context.Context, ArtifactRef) (*Artifact, error)
+}
+
 // ExecutionTarget represents effective model runtime settings.
 type ExecutionTarget struct {
 	Endpoint        string         `json:"endpoint"`