Expose a `nix run .#take-screenshots` app that runs a binary inside an
Xvfb display with lavapipe software Vulkan and captures PNG snapshots
via ImageMagick. Useful for smoke-testing the Bevy renderer in
environments without a GPU (CI, sandboxed shells, agents).
Usage:
nix run .#take-screenshots -- EXE NUM DELAY_START PAUSE_INBETWEEN [OUTPUT_DIR]
The script picks the first free :N >= 99, locates the lavapipe ICD via
pkgs.mesa with a fallback to /run/opengl-driver (NixOS), reuses the
dev shell's runtimeLibs in LD_LIBRARY_PATH, and traps EXIT for cleanup.
README updated with usage and a worked example.
Replaced direct buildInputs with LD_LIBRARY_PATH configuration to streamline dependency handling. This makes library paths explicitly managed and simplifies runtime linking for the required packages. Updated the devShells configuration accordingly.
