[Bug] "Decrease column size" requires 2 keypresses on certain size, in fractional scaling

[jinliu]

Karousel version: 0.15
Plasma version: 6.6 beta
X11 / Wayland: Wayland

Description:
For example, with a 3200x2000 screen at 250% scaling, and the following config:

Decreasing column width to the preset 75% would result in with 939, but kwin would adjust it to 939.2 so it falls in integer physical pixels at 2.5x scale. So at the next keypress, Karousel would again try to decrease the width from 939.2 to 939, with no visible change.