Created attachment 174130 [details]
screenshot of gap between taskbar and maximized window

SUMMARY
For panel height 42, there is gap between task bar panel and maximized window, so that colors of wallpaper can be seen. 

STEPS TO REPRODUCE
1. With panel at the bottom (all default, floating), set height to 42
2. Set some colorful background on your desktop to better see the issue
3. Open some dark program, i.e. Konsole, and maximize it

OBSERVED RESULT
There is 1px gap between taskbar and maximized window, wallpaper colors visible

EXPECTED RESULT
Bottom of maximized window should snap to taskbar without gap

SOFTWARE/OS VERSIONS
Operating System: Arch Linux 
KDE Plasma Version: 6.1.5
KDE Frameworks Version: 6.6.0
Qt Version: 6.7.2
Kernel Version: 6.10.10-arch1-1 (64-bit)
Graphics Platform: X11
Processors: 8 × Intel® Core™ i7-9700K CPU @ 3.60GHz
Memory: 15.6 GiB of RAM
Graphics Processor: NVIDIA GeForce RTX 4070/PCIe/SSE2