Fixed-Law Record-Reconstruction Closure Diagnostics: A Finite Z2 Lattice-Gauge Toy Lab

D2/R1 stands for Paper D2 / Reconstruction Module 1, with R meaning Reconstruction. This public working paper introduces a finite fixed-law Z2 lattice-gauge toy lab for access-limited record-reconstruction diagnostics. The goal is not to infer physics from a reduced model, but to make a record-reconstruction diagnostic explicit, reproducible, quotient-aware, and failure-capable in a declared finite law. For each protocol, the companion artifact specifies a finite record map, target map, quotient convention, exact inverse-bucket diagnostic decoder, and failure convention, and then exhaustively reports whether the declared finite-toy target is singleton-reconstructible or fails explicitly as noᵣecord, underdetermined, aliasing, quotientfail, or wrong. In the declared 2x3 torus, plaquette-only records leave four compatible orbit-label targets per record bucket; adding the two declared global closed-loop values makes the inverse target buckets singleton under the declared protocol; dropping one global loop restores ambiguity. The same finite rank/bucket diagnostic pattern is observed at a second declared finite size, the 3x3 torus. These are fixed-law finite-toy diagnostics only. The paper does not define a probability measure, Born rule, no-signaling law, actualization rule, physical selector, quantum-gravity model, or experimental prediction.