Stylix's qt target sets QT_STYLE_OVERRIDE=kvantum and writes qt6ct/qt5ct
configs with style=kvantum. plasmashell/KWin crash with a fatal
'module kvantum is not installed' QML error because the kvantum Qt style
plugin is not available in the Plasma session.
- stylix: targets.qt.enable = false (stops QT_STYLE_OVERRIDE=kvantum)
- plasma: remove kvantum package, add widgetStyle=Breeze as belt-and-suspenders
47d7d5b11e