The column guard is a claim about kwargs; "the value comes back" is a
different claim, and only a round trip settles it. This drives the real
`restore_full_backup` over a judged shape carrying all three of the columns
that were going missing.
`diverges_from` gets the harder assertion. It is a FK to notes.id, so the
tempting fix — carry the exported id across — produces a row pointing at
whatever note holds that number in the target database: not dropped,
REATTACHED, with the restore reporting success and the divergence about the
wrong snippet. So the test asserts WHOSE note the pointer landed on rather
than which integer it holds, and it refuses to run at all if the restore
happened to reuse the source id, which would let it pass without proving
anything. Same shape as the assertion in the rule_usage round trip, for the
same seam.
Also corrects this module's own docstring, which said the round-trip module
"is not written yet". Three existed; this is the fourth.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01821k5B3Ysecp9fNYs92Kuy
