Reported as "the port has low FPS". Godot 4 renders through Vulkan and this
launcher passed nothing through, so it fell back to lavapipe: software Vulkan,
correct and slow. The decoder's launcher has had this block for a long time;
the container that actually runs a renderer was the one without it.
Same three cases as the decoder, including the part worth repeating: passing
/dev/dri alone does NOT work for NVIDIA -- Mesa cannot drive the card and the
proprietary userspace lives outside the image. It needs the container toolkit.
The NOTE now prints the full repo-add sequence, because the package is not in
Ubuntu's default repos and `apt install nvidia-container-toolkit` on its own
fails with 'no installation candidate' -- which reads like the package is
wrong rather than the source being missing.
47207a1474