Data Summary DTO
@Serializable
Wire-safe summary of the data series that was fit: the full StatisticIfc summary (statistics) plus the sign/zero counts the fitting EDA needs (which StatisticData does not carry). The dataset-level left shift is reported separately in ShiftAnalysisDTO (continuous) — it is not a statistic.
Although a client that supplied the raw data could recompute these, the summary is returned so the result reflects the engine's exact statistics (and so a thin client need not recompute anything).