A single consolidation migration replaces the 150 removed historical files.
It decides — from reads alone — whether to build the boundary schema fresh,
skip on a fully-migrated 2.x database, or refuse a partial or inconsistent
history untouched. Fresh installs run it first and the live v3 chain after;
pre-2.x installs are directed through the latest 2.x release. The same
verdict backs a self-updater preflight so an unsafe upgrade is refused
before any file is copied. Schema verified identical to the boundary
fixtures on SQLite, MariaDB and PostgreSQL.
