3.1.0

Added

• temporal.add_calendar_columns, with second_of_day, second_of_week and day_of_week: a pure UTC calendar decomposition of an Int64 Unix-seconds column. second_of_day and second_of_week place a timestamp inside the UTC day and the UTC week (Monday 0 through Sunday 6); add_calendar_columns turns both into four cyclic columns, cal_mod_sin, cal_mod_cos, cal_dow_sin, cal_dow_cos, so the day and week wrap without a discontinuity. The clock is UTC by construction: there is no timezone parameter, and a Datetime column is refused rather than converted. The column must be exactly Int64, and existing columns of the same names are refused rather than overwritten.

Purely additive: no existing name, column or signature changes since 3.0.0. Specified by ADR 008 (calendar features and regime context).