Benchmark evidence

Only campaigns that code or specs cite live here:

• swiglu-x4-2026-09-05 — cited by crates/wh-iron-std/src/kernels/ops/gated_activation.rs
• nax-bt-split-2026-09-06, nax-ld40-2026-09-06, nax-wide-2026-09-06 — the nax-* evidence format docs/specs/TENSOROPS_PRIMITIVE.md points at (predeclared gate, paired rounds, forward+reverse arm order, F64 oracle, mutation negative, frozen hashes, losses reported alongside wins)

Each keeps its README.md, small summary json/csv, and SHA256SUMS as the fingerprint of the raw runs. Raw evidence (*.csv.gz, *.log.gz, evidence.tar.gz) and campaign logs that nothing references are not kept in git — .gitignore blocks the raw formats, and a campaign’s numbers belong in the PR body that landed the change. If a spec or kernel doc comment later needs to cite a campaign, add just that campaign’s summary here and link it from the citing file. History before 2026-09-08 holds the removed material.