SPARC Environment Proxy + RC-Fit η-Limit — LOCKED Evidence Pack (2026-01-21)

This record provides a locked, downloader-ready evidence pack for a SPARC rotation-curve (RC) fit workflow extended with an external environment proxy. The package includes an env-proxy robustness grid producing σ_env (dex), a hardened σ_env → η policy ceiling, and an empirical SPARC RC-fit η-limit derived from an η scan under explicit fit-degradation thresholds. The main result is that RC-fit compatibility yields a conservative bound η_max,allowed ≈ 0.08, while the policy-implied ceiling over the tested σ_env band is typically higher (of order 0.18–0.20). All artifacts are generated under a strict NO-OVERWRITE workflow and include SHA256 integrity checks. Integrity verification (downloader perspective): tar -xzf SPARC_ENVPROXY_POLICY_RCFIT_LOCKED_PACK_20260121_212909.tar.gz cd SPARC_ENVPROXY_POLICY_RCFIT_LOCKED_PACK_20260121_212909 sha256sum -c PACK_SHA256SUMS.txt