Pulls closed as already on the base before 4e481725 stop counting as landed in the vitals and home KPIs #8738

Left out of #8628 (pull #8631, 4e481725): new pulls closed as already on the base no longer count as landed, but the past ones (97 in five minutes on 0.7.332) were not backfilled, so opened/landed still includes them.

Done looks like:

• [x] A one-shot migration marks the earlier closed-as-already-on-the-base pulls the same way 4e481725 marks new ones, so readVitals and the home KPIs exclude them.
• [x] A test seeds old pulls of that kind and real landings; after migrating, only the real landings count.

Files: src/core/migrations/<new>.ts, src/flow/kpis.ts, src/flow/vitals.ts, a test beside them Risks: a real landing wrongly excluded. Match exactly the close reason 4e481725 records, never a heuristic on titles.

Reviewed pull #8759 at its head: ticked A one-shot migration marks the earlier closed-as-already-on-the-base pulls the same way 4e481725 marks new ones, so readVitals and the home KPIs exclude them.; A test seeds old pulls of that kind and real landings; after migrating, only the real landings count..