perf: all Base17 ops multi-versioned SIMD — AVX-512/AVX2/scalar via LazyLock

4 functions converted to multi-versioned kernels:
  l1_weighted:     I32x16 mul(abs_diff, weights) + reduce_sum
  sign_agreement:  I32x16 xor + cmpge_mask + count_ones
  xor_bind:        I32x16 xor + cvtepi32_epi16 pack-back
  inject_noise:    I32x16 add(dims, prng_noise) + clamp

Pattern: #[target_feature(enable = "avx512f")] per-function,
LazyLock runtime detection, one binary serves all ISAs.

No global target-cpu in .cargo/config.toml.
CI (AVX2) and Production (AVX-512) use same binary.
629M lookups/sec, 19K tokens/sec, 19 tests passing.

https://claude.ai/code/session_01M3at4EuHVvQ8S95mSnKgtK

Author: claude