- Add stub implementation in nvml_gpu.cpp when NVML not available
- CMakeLists.txt checks for both NVML library and headers
- Build succeeds on macOS/non-NVIDIA systems with stub
- Runtime detection via gpu_is_available() prevents runtime errors
- Add native/nvml_gpu/ C++ library wrapping NVIDIA Management Library
- Add Go bindings in internal/worker/gpu_nvml_native.go and gpu_nvml_stub.go
- Update gpu_detector.go to use NVML for accurate GPU count detection
- Update native/CMakeLists.txt to build nvml_gpu library
- Provides real-time GPU utilization, memory, temperature, clocks, power
- Falls back to environment variable when NVML unavailable
