Rows that keep their order slide to their new places; rows that change
order, leave or arrive fade out toward and in from the middle of their
path, so no text ever crosses. Boxes gain a paint inset, which page tabs
use to leave an even gap under each tab while the whole row still takes
the pointer, and the open tab's inner corners are concentric with its
neighbours'.

Assisted-by: claude-opus-5.5
Assisted-by: claude-opus-5