aKeyAlreadyInsideTheSafeSetStillFindsItsOwnFile

The one case where reading a legacy file is correct: the key was already inside the safe set, so both schemes are the identity on it and the "orphan" is that key's own file. spans and span-state carry over for free.

This is the complement of aKeyNeverAdoptsAnotherKeysLegacyOrphan and it needs no separate plant-landed assertion: presence is what it asserts, so a plantRawFile that wrote nothing reds it directly.

Note these two are fixtures, not shipped keys. Every key kuilt itself stores contains a ., so every one of them moves and loses its data; the carry-over benefits consumers whose key names happened to be inside [a-z0-9-].