Definitional asynchrony of Japan's secondary medical areas across national data products (Akita 8→3 reorganization): validated crosswalk, reconstruction code, and timeline

Companion deposit for the preprint "When statistics outlive their geography: asynchronous propagation of a secondary medical area redefinition across Japan's national health data infrastructure — a measurable instance of institutional debt" (medRxiv). Contains the validated municipality–SMA crosswalk (current 3-SMA definition, 330 SMAs), the reconstructed superseded 8-SMA layout of Akita Prefecture with structural validation code, observed/expected patient counts for the eight superseded zones backing the mis-join magnitude figures, a machine-readable timeline of the redefinition's asynchronous propagation across the 11th NDB Open Data, the Physician Statistics 2024, and the MHLW correspondence table, and the preprint figure (EN/JA). Documents two join-failure modes: five detectably unmatched codes and three codes reused across definitions (silent mis-join).