Run world-load checks and migrations (GM-only). First reports any surviving
legacy trait documents (retired in #651, never auto-converted), then — on the
active GM only, to avoid multiple GMs racing to write — runs the version-keyed
migration and advances the stored systemMigrationVersion.
Run world-load checks and migrations (GM-only). First reports any surviving legacy
traitdocuments (retired in #651, never auto-converted), then — on the active GM only, to avoid multiple GMs racing to write — runs the version-keyed migration and advances the storedsystemMigrationVersion.