BasisSimulator.jl: GPU-native polychromatic CT and PCCT simulation, reconstruction, and virtual monoenergetic imaging in Julia

GPU-native Julia framework for CT and photon-counting CT simulation, reconstruction, and quantitative spectral imaging. Provides exact Siddon ray-tracing forward projection, polychromatic Beer-Lambert physics with vendor-realistic detector response (MC-derived LUTs for GE Gemstone scintillator and Siemens NAEOTOM Alpha CdTe), FDK and hybrid iterative reconstruction, sinogram and image-domain beam-hardening correction, dual-kVp and PCCT material decomposition (Cong 2022, Alvarez-Macovski, PWLS), and virtual monoenergetic imaging (VMI + Grant 2014 Mono+) — all dispatching transparently across CPU, Metal, CUDA, and ROCm via AcceleratedKernels.jl.