Run the audit archive cron when :nexus or :admin-console is on. Ship
allowlisted events to Admin Console first (with row ids for
idempotency), then the full chunk to Nexus when :nexus is set. Mark
archived_at for the whole chunk on success, including nitrate-only
mode. Rename the gate flag from :audit-log-archive to :nexus.
AI-assisted-by: Composer
Co-authored-by: Cursor <cursoragent@cursor.com>
