Computes three signed metrics per window from the underlying
        forensic windows analysis:
          - slip_velocity_days_per_day: completion shift / window
            duration (positive = slipping, negative = recovering).
            Numerator is the WORKING-day completion shift. The
            denominator is WORKING days between the prior and later
            data dates on the same calendar
            (``window_duration_workdays``), making this a same-day-type
            working-day/working-day rate. It falls back to CALENDAR days
            only for legacy window dicts that predate that field, and
            such a row is flagged ``velocity_basis="wd/cd"``. Read
            ``velocity_basis`` to know which denominator produced the
            figure.

            Each velocity field name states the ratio it holds:
            ``slip_velocity_workdays_per_workday`` (populated only on
            the wd/wd path), ``slip_velocity_workdays_per_calendar_day``
            (working-days of slip per CALENDAR day elapsed, computed
            against ``window_duration_days``), and
            ``slip_velocity_days_per_day`` as the retained back-compat
            name for whichever basis was selected. Quote ``basis`` in
            any expert report.

            NOTE (2026-09-03): the two named fields are no longer equal.
            ``slip_velocity_workdays_per_calendar_day`` used to be a
            blind copy of the headline velocity, which made its name
            wrong once the denominator moved to working days — it read
            5/10 = 0.500 while its name promised 5/14 = 0.357. It now
            holds the calendar-day rate it is named for.
          - slip_acceleration: velocity[n] - velocity[n-1] (positive
            = slip rate increasing, negative = decelerating/recovery)
          - half_period_estimated_slip_days: shift / 2 (forensic
            "where were we at the midpoint" centroid estimate), in
            WORKING days

        Cumulative aggregates ``mean_velocity_days_per_day`` plus a
        mean per basis — ``mean_velocity_workdays_per_workday`` and
        ``mean_velocity_workdays_per_calendar_day`` — each computed
        only from the rows that actually carry that denominator, so a
        mean is never labelled with a basis it did not use (None when
        no window carried it). ``velocity_basis_set`` lists the bases
        present and ``velocity_units`` describes them, including an
        explicit MIXED string when a run spans both.
        Also ``max_velocity_window`` and accelerating / decelerating /
        recovery window counts.

        Honest caveats embedded in the response (mandatory for expert
        reports): midpoint estimates are probabilistic centroids, not
        observed events; velocity is per-window average, not
        instantaneous; acceleration is a finite difference, not a true
        second derivative.

        Built on top of AACE RP 29R-03 §3.3 windows analysis. Use this
        tool when you want a slip-rate trend line on top of the same
        per-window math ``forensic_windows_analysis`` already computes.

        Args:
            schedules: chronologically ordered list of dicts — the SAME
                shape ``forensic_windows_analysis`` accepts. Each dict
                carries ``label`` (optional) and EXACTLY ONE of
                ``xer_content`` or ``xer_path``. Preferred input for
                hosted/remote clients.
            xer_paths: legacy chronologically ordered list of server-side
                XER paths.
            xer_contents: legacy chronologically ordered list of XER text
                contents (alternative for hosted/remote use).
            Supply EXACTLY ONE of schedules / xer_paths / xer_contents
            (at least 2 entries).

        Returns:
            {
              "rows": [{window_label, period_start, period_end,
                        window_duration_days, shift_days, shift_workdays,
                        shift_calendar_days,
                        velocity_basis,
                        slip_velocity_days_per_day,
                        slip_velocity_workdays_per_workday,
                        slip_velocity_workdays_per_calendar_day,
                        velocity_field,
                        velocity_units, slip_acceleration,
                        acceleration_units, midpoint_estimate_date,
                        half_period_estimated_slip_days,
                        half_period_estimated_slip_workdays,
                        half_period_units}, ...],
              "cumulative": {mean_velocity_days_per_day,
                             mean_velocity_workdays_per_workday,
                             mean_velocity_workdays_per_calendar_day,
                             velocity_basis_set,
                             velocity_units, max_velocity_window,
                             accelerating_windows,
                             decelerating_windows,
                             recovery_windows},
              "units": "working-days of slip per working-day elapsed"
                       " (wd/cd fallback wording on legacy windows;
                       "  MIXED when a run spans both)",
              "basis": "<numerator/denominator day-type disclosure>",
              "standard": "AACE RP 29R-03 §3.3 (Windows Analysis)",
              "caveat": "..."
            }