0.9.6.30 — rebalancing a bucket forgot the column's bounds

Fixes a defect where re-hitting a monthly total after realism ran would silently undo the column's declared min/max. An integer payroll column declared 45,000 to 350,000 could hold values of 1,808 or 815,895 while every monthly aggregate stayed exact. Covered by a new regression test; full suite at 1,890 passing.