fix(iterator): surface blob listing errors for better diagnostics (#1017)

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

abs/replica_client.go

@@ -394,7 +394,7 @@ func newLTXFileIterator(ctx context.Context, client *ReplicaClient, level int, s
 func (itr *ltxFileIterator) Close() (err error) {
 	itr.closed = true
 	itr.cancel()
-	return nil
+	return itr.err
 }
 
 func (itr *ltxFileIterator) Next() bool {

nats/replica_client.go

@@ -503,7 +503,7 @@ func (itr *ltxFileIterator) Err() error {
 	return itr.err
 }
 
-// Close closes the iterator.
+// Close closes the iterator and returns any error that occurred during iteration.
 func (itr *ltxFileIterator) Close() error {
-	return nil
+	return itr.err
 }

oss/replica_client.go

@@ -501,11 +501,11 @@ func (itr *fileIterator) initPaginator() {
 	})
 }
 
-// Close stops iteration.
+// Close stops iteration and returns any error that occurred during iteration.
 func (itr *fileIterator) Close() (err error) {
 	itr.closed = true
 	itr.cancel()
-	return nil
+	return itr.err
 }
 
 // Next returns the next file. Returns false when no more files are available.

s3/replica_client.go

@@ -1166,11 +1166,11 @@ func (itr *fileIterator) fetchMetadataBatch(keys []string) error {
 	return nil
 }
 
-// Close stops iteration.
+// Close stops iteration and returns any error that occurred during iteration.
 func (itr *fileIterator) Close() (err error) {
 	itr.closed = true
 	itr.cancel()
-	return nil
+	return itr.err
 }
 
 // Next returns the next file. Returns false when no more files are available.