Preserve an Ubuntu/NVIDIA Affinity v3 launch path and expose it in the GUI

[hnoerenberg]

Summary

This change adds a small preserved launcher path for Ubuntu-family + KDE/Wayland + NVIDIA setups
and wires it into the Python GUI so the same runtime path can be reused from the menu, desktop
launcher, and an explicit launch action.

What changed

• added AffinityScripts/AffinityUbuntuLauncher.sh
• added a GUI action to launch Affinity v3 through the preserved Ubuntu snapshot path
• added a GUI action to install desktop launchers that point at the preserved snapshot script
• updated the unified Affinity.desktop creation path to prefer the snapshot launcher when present
• reused the same Vulkan runtime environment when creating desktop launchers and when launching
  Affinity directly from the GUI
• disabled VK_KHR_present_id and VK_KHR_present_wait on Wayland (via VKD3D_DISABLE_EXTENSIONS)
• set VKD3D_CONFIG=swapchain_legacy on Wayland + NVIDIA
• added documentation for the launcher snapshot in docs/LEGACY-SCRIPTS.md

Why

On Ubuntu-family / KDE Plasma (Wayland) / NVIDIA setups Affinity v3 was only stable once the
launch path consistently:

• ran Affinity directly instead of going through wine start
• kept the Wine/X11 driver active under Wayland (HKEY_CURRENT_USER\Software\Wine\Drivers → x11)
• used the known-good NVIDIA Vulkan environment (__NV_PRIME_RENDER_OFFLOAD, MESA_VK_DEVICE_SELECT)
• disabled VK_KHR_present_id and VK_KHR_present_wait on Wayland

Before this change, the GUI launch path and the generated desktop entry could diverge, which made
it easy to lose a working configuration after an update.

Tested on

• TUXEDO OS 24.04.4 LTS (Ubuntu-family, ID_LIKE="ubuntu debian")
• KDE Plasma 6.6.5 on Wayland
• NVIDIA GPU (driver 580.178.04, open kernel module)
• ElementalWarrior Wine 10.20 (Staging)
• Affinity v3 unified application — starts reliably, main window detected

Validation

• python3 -m py_compile AffinityScripts/AffinityLinuxInstaller.py — no errors
• bash -n AffinityScripts/AffinityUbuntuLauncher.sh — no errors
• bash AffinityScripts/AffinityUbuntuLauncher.sh status — correct Wine/GPU/Wayland detection
• bash AffinityScripts/AffinityUbuntuLauncher.sh launch — Affinity v3 starts successfully
• GUI installer opens with both "Launch Affinity v3" and "Launch Affinity v3 (Ubuntu Snapshot)"
  buttons visible and functional

Notes

• This PR intentionally excludes local probe binaries, DLL experiments, and broader installer
  changes from the author's working tree.
• If preferred, the snapshot script can be discussed as a separate PR from the GUI wiring.
• The PR is rebased onto upstream main as of 9b3e84b ("Fix weird font issues", 18 Aug 2026).