_validate carried the whole matrix in one function (cc C/13, over the
branch quality gate). Splitting it by what is actually being checked —
shared, sqlite-only, postgres-only — puts every piece at A/B.
Ordering is the part that had to survive: the chain's order is the error
messages' priority, so a run with several bad flags still reports the
same one it did before. The --vacuum/--apply pairing therefore stays in
the shared step ahead of the backend branch, where it was; it is a "do
not rewrite the whole file when you only meant to look" rule, which
holds before the question of which backend a flag belongs to.
No behavior change: all nine parser.error strings are byte-identical and
in the same order, and the eight usage-error cases pass unmodified.
iomgaa
4b06093d6c