When a keyword was renamed or merged, the keyword filter followed it by
cutting the old name off by bytes: names match whatever their case, and
where a letter's case changes its length (ẞ / ß) the cut could land
inside a letter and panic (`ẞẞA` → `Road` with the filter on `ßßa|é`).
It now uses the catalog's level-based `reparent`.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>