VolumeEcShardsGenerate updated for generation-specific file creation

weed/shell/command_ec_encode.go

@@ -262,6 +262,7 @@ func generateEcShards(grpcDialOption grpc.DialOption, volumeId needle.VolumeId,
 		_, genErr := volumeServerClient.VolumeEcShardsGenerate(context.Background(), &volume_server_pb.VolumeEcShardsGenerateRequest{
 			VolumeId:   uint32(volumeId),
 			Collection: collection,
+			Generation: 0, // shell commands operate on existing (generation 0) volumes
 		})
 		return genErr
 	})