[Linux] Verify: reports carried over from window_manager

Start with a Flutter app using the Window API and reproduce the nine linked window_manager reports on Linux, including the listed desktop environments and embedding case. Check off each report after confirming it, fixing it, or recording that it no longer occurs.

These were reported against window_manager 0.5.x, whose platform code is gone: window_manager 0.6.0 is rebuilt on nativeapi. None of them has been checked against nativeapi yet. Each needs a reproduction with nativeapi (a Flutter app on the Window API), then a fix or a note that it no longer happens. Tick them off here as they're checked.

• leanflutter/window_manager#167: full screen doesn't work (Arch Linux)
• leanflutter/window_manager#535: in full screen, each hide/show shifts the window further off-screen
• leanflutter/window_manager#179: transparent background colour renders black (Arch, KDE Wayland)
• leanflutter/window_manager#370: a longer title set before showing is ellipsized to the original length until resize
• leanflutter/window_manager#411: setSize has no effect (Hyprland, Ubuntu 22.04)
• leanflutter/window_manager#427: onWindowResize fires in an endless loop
• leanflutter/window_manager#497: window visibly repositions on start
• leanflutter/window_manager#519: black window when the app runs as a GTK_PLUG (embedded in another app)
• leanflutter/window_manager#561: title bar glitches with min/max size or setResizable (KDE Plasma 6 Wayland, NVIDIA)