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

internal/modules/dnd/extract/spells/extractor_test.go

@@ -117,6 +117,10 @@ func TestExtractPromptUsesCanonicalOverlayNamesWithoutAliasesOrMetadata(t *testi
 	if got, ok := metadata["catalog_overlay_ids"].([]string); !ok || !reflect.DeepEqual(got, []string{"campaign.example"}) {
 		t.Fatalf("catalog overlay metadata = %#v", metadata["catalog_overlay_ids"])
 	}
+	fingerprints := newExtractor(t, &fakeSpellsLLMClient{}, overlaySpellCatalogReference()).CheckpointFingerprints()
+	if len(fingerprints) != 1 || fingerprints[0].Name != "effective_catalog" || fingerprints[0].Value != metadata["catalog_digest"] {
+		t.Fatalf("checkpoint fingerprints = %#v, want manifest catalog digest %#v", fingerprints, metadata["catalog_digest"])
+	}
 	encoded, err := json.Marshal(metadata)
 	if err != nil {
 		t.Fatal(err)