NO_CHANGES is a first-class outcome rather than an empty duplicate
draft — a re-run with nothing new must say so, not mint one.
A week holds one entry, so every merge outcome names what the merge
touched. MERGED_INTO_PUBLISHED is separate from MERGED because the
entry it grew is already in front of customers: the operator is editing
live copy, not a draft, and nothing else on the response says so.
MERGED_AFTER_DIGEST narrows that again to a week some digest has
already claimed. Claiming is what makes an entry unmailable a second time,
so bullets appended afterwards reach no send unless somebody puts them
there — reported, because the alternative is losing them quietly.