Persist diagnostics in reusable pipeline state

internal/framework/chunkplan/store.go

@@ -14,6 +14,7 @@ import (
 	"syscall"
 
 	"gitea.maximumdirect.net/eric/notarius/internal/core/source"
+	"gitea.maximumdirect.net/eric/notarius/internal/framework/contracts"
 	"gitea.maximumdirect.net/eric/notarius/internal/framework/pipeline"
 )
 
@@ -340,6 +341,9 @@ func validateRecord(record pipeline.ChunkPlanRecord, requestedDigest string) err
 	if record.SchemaVersion != SchemaVersion {
 		return fmt.Errorf("schema_version %q is not supported", record.SchemaVersion)
 	}
+	if err := contracts.ValidateProducerDiagnostics(record.Diagnostics); err != nil {
+		return fmt.Errorf("diagnostics: %w", err)
+	}
 	if _, err := digestPathSegment(requestedDigest); err != nil {
 		return err
 	}