is_cuda_server() treats a co-located libggml-cuda.so* as proof the server is
CUDA-ready. That's normally true (llama.cpp dlopens the backend from beside the
binary), but an *interrupted* build (thermal/power shutdown -- common on the
NVIDIA-ARM laptops this path targets) can leave a half-linked libggml-cuda.so
next to the server: present, so is_cuda_server() matches, yet the backend fails
to load at runtime. The post-build path already wipes+rebuilds such a partial
.so, but the step-0 early-skip trusted it and never rebuilt -- so Studio could
report GGUF CUDA inference ready while running a broken/non-CUDA backend.
Gate the early-skip with cuda_server_probe(): 'llama-server --list-devices'
enumerates backends and exits (cheap, no server spin-up). Only a definitive
'flag supported, ran, but no CUDA device' triggers a clean rebuild; a timeout or
an old pin without --list-devices stays inconclusive and keeps trusting the .so,
so we never force a needless, thermally-expensive rebuild. Probe logic verified
against healthy/broken/unsupported/timeout stubs (0/1/2/2).
Addresses Codex review P2 (provision_llama_cuda.sh).
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