fix: redesign benchmark integrity foundation

[AlexU-A]

Summary

• migrate all 24 React, Next.js, and React Native fixtures to strict schema v2 with explicit public context and private adjudication
• add five intentional-clean controls and correct unsupported framework gold claims
• expose complete public rule definitions while limiting the candidate treatment to inline committed SKILL.md
• execute the scorer from exact committed bytes and strengthen capture, schema, metric, and publication-substitution tests
• retain descriptive-only boundaries: this includes no provider captures, performance result, full-skill claim, or statistical-superiority claim

Verification

• PYTHONDONTWRITEBYTECODE=1 python3 -m unittest discover -v — PASS, 27 tests in 34.197s
• python3 -B scripts/verify_no_copied_skills.py — PASS, 4 manifests and 32 unique skills
• python3 -B scripts/run_benchmark.py --help — PASS from committed scorer blob
• git diff --check — PASS before commit
• python3 -B scripts/aggregate_stability.py — expected exit 1 with the retired-window notice

Known merge blocker

Do not merge this draft yet. Independent review reproduced a remaining publication race in scripts/benchmark_scorer.py::atomic_publish: another directory can replace the just-created public bundle between bundle.mkdir() and the first bundle.lstat(). The replacement can then be accepted as the reservation, overwritten, and marked COMPLETE.

A fresh bounded follow-up should replace pathname reservation with complete staging plus an atomic no-replace directory rename (renamex_np(..., RENAME_EXCL) on macOS and renameat2(..., RENAME_NOREPLACE) on Linux), fail closed elsewhere, add creation-to-publish race regressions, and receive a fresh independent test-critic review.

CI status

GitHub's validate job currently fails in the unchanged python3 scripts/refresh_external_skills.py --check step because upstream pins have moved for 39 external skill entries and many configured raw-content paths now return HTTP 404. This branch does not change the external-skill manifests. The focused unit, manifest-structure, and committed-bootstrap checks above pass locally; the existing external-refresh drift remains separate from the publication-race blocker.