SΔϕ-81 — UMR Is Not Null: Unmeasured Remainder, Epistemic Non-Erasure, Machine Serialization, and Re-entry (v1.0, AI-Native Package)

SΔϕ-81 formalizes UMR (Unmeasured Remainder) as an explicit epistemic state for cases in which available evidence and model capacity do not justify a determinate assignment, while that lack of determination also does not justify assigning absence, falsity, zero, non-applicability, or presence. It establishes the canonical invariant `UMR ≠ NULL`, introduces epistemic non-erasure, typed epistemic states, re-entry rules, machine serialization requirements, misclassification rules, audit protocol, evaluation cases, and a JSON schema. The central protective proposition is: “Absence of resolution must not be serialized as absence of being.”