breathe-store

The durable-store seam for breathe — DecisionLog (the single counter-accumulation fold + the append-only decision feed) + SampleCache (the predictive prior sample). An in-memory tier (today, byte-identical to the CRD-status projection) and (M2/M3) a Postgres/Redis tier behind the same `&dyn` seam: one config switch selects the backend; the band law and reconcile loop never change. See docs/BREATHE-MICROSERVICE.md.