v1.4.30 backstop. Every new endpoint introduced earlier in the patch
run rides the existing real-Postgres container fixture (v1.4.29's
contribution): the SyncMode handshake, the mood-entries bulk
upsert, the medication-intake bulk insert with idempotency-key
collision, the mood-note column round-trip, and the drain helper
itself.
This commit adds the missing slot — the admin endpoint
POST /api/admin/drain-per-sample-cumulative — so the route's admin
gate, dryRun default, and commit path all run against real SQL
end-to-end. Mocked-prisma siblings would have hidden the v1.4.29
lesson (the date_trunc bound-parameter bug); the route's
transactional upsert + delete needs the same fence.
Coverage delta: 3 new integration specs, all green.