- tablekit builds a filter row under the headers for every th with data-filter;
distinct cell values become a select (label from data-filter-label), or a
text substring filter with data-filter="text"
- filters combine with the global table search; placeholder rows (colspan) are
not filtered away; filter row follows the lab-focus column hiding
- enabled on: matrix lab columns (by variant), defense table (ЛР, status with
readable values), students (Основа, Пароль), lab assignment lists (Уровень,
Источник, Сдача), labs list (Статус)
