Summary

• Update `find_package(lux-gpu CONFIG REQUIRED)` -> `find_package(lux-gpu-rt CONFIG REQUIRED)` to track the upstream package rename (rename: lux-gpu -> lux-gpu-rt lux-gpu#1).
• Link target `lux::lux_gpu_core` -> `lux::gpu-rt`.
• Bump `luxaccel` version 0.1.1 -> 0.1.2 to signal the dependency rename. C ABI is unchanged.

Test plan

• `cmake -B build -DCMAKE_PREFIX_PATH=/path/to/lux-gpu-rt-install && cmake --build build` builds `libluxaccel.0.1.2.dylib` clean.
• `otool -L` shows only stdlib + system deps (gpu-rt symbols absorbed statically, hidden visibility).
• Codesigned ad-hoc for macOS.