* Select Apple Metal 4.0.1 kernel; keep 4.0.0 u64 elsewhere
NVIDIA was ~37% slower on the 4.0.1 Metal-tuned kernel. Split
Poseidon2 kernels and pick by backend:
- Metal + SHADER_INT64: v4.0.1 u64
- other SHADER_INT64: v4.0.0 u64
- no SHADER_INT64: 32-bit fallback (same as 4.0.0)
CI uploads the Linux release binary as an artifact so we can
bench NVIDIA without building on the GPU box.
* Drop version numbers from GPU kernel labels
Log native-u64 vs native-u64 Apple Metal without tying
the strings to release tags.
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