Extend build.rs to compile all 25 .cu kernel files to cubins via nvcc.
Common header prepended to 24 kernels; experience_kernels.cu is standalone.
Total cubin size ~1.1 MB embedded in binary.
- cargo:rerun-if-changed tracks all .cu and .cuh files
- CUDA_COMPUTE_CAP env var selects target arch (sm_86, sm_90)
- Graceful skip when nvcc unavailable (non-CUDA builds)
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>