An Operational Length Anchor D: Identifiability, Cross‑Invariants, and an Adoption Algorithm — Source & Data (v1.0)

What this is. A fully reproducible Source & Data package for the paper "An Operational Length Anchor D: Identifiability, Cross-Invariants, and an Adoption Algorithm." The work introduces a fit-free acceptance rule for adopting a realization-independent length anchor D. D: Adopt iff all gates pass and the CI-intersection holds, IA intersect IB intersect IC != empty_set, with a diameter bound (95% coverage; Bonferroni per-interval 1 - alpha / m). Pipelines Pi_A (transverse spectral spacing) and Pi_B (axial modal peak) are informationally complementary yet converge to the same anchor D once gauge is fixed; Pi_C evaluates target lambda_target / r_hat. The MODE (m=1) gate operationalizes the Identifiability Theorem by excluding m >= 2 via an O(10^-1) A/B discrepancy, far above the nominal thresholds. SI anchoring is verified with R_CROSS on 633 nm / 532 nm lines.