## Summary
Two threads on the run-ops split path.
Read path: per-item run reads are batched into grouped queries, a
waitpoint's connected-run reads are bounded, and the dedicated-schema
relation hydrators fetch only the requested columns instead of whole
rows. Retrieve also falls back to the other database when a routed read
misses, so a run whose physical residency diverges from its id shape is
still found rather than returning a spurious not-found. Fewer and
lighter queries on the run read path, with no change to results.
Mint-kind flip safety: flipping which database new runs mint to is now a
deterministic wall-clock cutover, for both per-org and global flips. For
a grace window every process resolves the same database, so a flip
cannot route two concurrent triggers that share an idempotency key to
different databases (which would bypass the per-database unique
constraint and create a duplicate run).
Supersedes the earlier #4205 and #4208.
Draft: validation in progress.
Daniel Sutton
c601739d35