Add independent SageMath certificate validation

[kabudu]

Summary

• add a separate SageMath 10.6 implementation for finite Hamming and Rankin rows
• publish a 27-row deterministic differential corpus with certificates, hashes, environment versions, and exact results
• regenerate the corpus in CI and distinguish QATQ checking, separate-software reproduction, and external human review

Why

QATQ v0.4.0 certificates were independently checkable by the built-in checker, but had not been reproduced by separate software. This patch strengthens the evidence without changing certificate semantics or the theorem surface.

Validation

• 27/27 QATQ certificates VALID and independently reproduced by SageMath
• 5 focused SageMath tests, including false witness and false objective rejection
• cargo fmt/check/test all features
• 84.89% line coverage
• RustSec audit and duplicate dependency check
• 4,096-case KV stress matrix
• public production and competitive compression gates
• cargo package and cargo publish --dry-run

Claim boundary

No theorem identifiers, schemas, codec formats, or runtime behavior change. No external human review is claimed; the machine-readable review status remains NOT_REVIEWED.