Add a framework mechanism for prepared modules and validators to contribute checkpoint identity fingerprints

internal/framework/pipeline/checkpoint.go

@@ -16,6 +16,13 @@ type CheckpointFingerprint struct {
 	Value string `json:"value"`
 }
 
+// CheckpointFingerprintProvider supplies stable, non-secret semantic identity
+// for a prepared module or validator. Values must not contain source content,
+// credentials, local paths, timestamps, or other invocation-specific data.
+type CheckpointFingerprintProvider interface {
+	CheckpointFingerprints() []CheckpointFingerprint
+}
+
 type CheckpointRecorder interface {
 	SourceRunning(moduleKey string) error
 	SourceSucceeded(moduleKey string, doc *source.SourceDocument) error