Split/tools bootstrap

[simonevadi]

Add a bootstrap script to prepare a local development environment for rayx. The script:

• checks that uv is available
• updates the git submodules
• creates or reuses .venv with Python 3.12 by default
• installs rayx in editable mode with uv pip install -e .

By default, the script asks whether the build should use NVIDIA/CUDA support. If you just press Enter, it builds with NVIDIA support enabled.

Available flags:

• --with-nvidia or --nvidia: build with NVIDIA/CUDA support
• --without-nvidia or --no-nvidia: build without NVIDIA/CUDA support
• --help: show the bootstrap usage message

When NVIDIA mode is enabled, the script checks for nvidia-smi and nvcc before starting the build. When NVIDIA mode is disabled, it passes -DRAYX_ENABLE_CUDA=OFF so the build proceeds without CUDA.

After completion, the development environment is ready to use. Activate it with:

source .venv/bin/activate

At the same time, the rayx makefile makes cuda optional so that the rayx-python project can be developed also on machines without nvidia.

[Atraxus]

I agree with the changes mostly, we definitely need to lower the hurdle to start developing rayx-python. I have some notes:

1. The install_nvidia reference is somehting I would either move to the docs or remove entirely to keep the project root clean.
2. I noticed HDF5 as a build requirement, which is not yet mentioned in our README
3. I've drafted a README that includes the requirements and build steps in one place — install instructions, dependency list (including HDF5, now labeled as a hard requirement with a link to the HDF5 docs rather than a walkthrough), and both build paths (CMake in-place, uv pip install -e .). Maybe that would work as a middle ground?

README.md

Feel free to merge after considering these