Constant RETIREMENT_TOMBSTONE_SOURCE 

const RETIREMENT_TOMBSTONE_SOURCE: &str = "operator_config_seed_retired";

The source sentinel bundle_delete_system_if_owned stamps on the tombstone version row it appends after deleting a row — distinguishes a deliberate, generation-aware retirement (pruned because a manifest no longer lists this id) from an ordinary human delete in Memory (bundle_delete_system, which records no version at all). bundle_ reseed_system_if_owned’s missing-row branch checks for this sentinel specifically — see that method’s own doc comment.