Phase 1 of docs/ALERT_ENGINE_EVOLUTION.md. internal/alerts/reducer is a
pure transition core for the metric-threshold family — hysteresis
trigger/clear, sustained-for delay with dip reset, warning/critical
severity derivation with the percentage 99-cap — characterized from
Manager.checkMetric, with time entering only through the signal's
ObservedAt so every sequence is deterministic and replayable.
reducer_parity_test.go drives the live manager and the reducer through
identical observation sequences (simulated time via the established
pending-backdate trick) and fails on any divergence after every step,
with the manager as the reference. The harness proved itself on its
first run by catching the stale-resolve defect fixed in the previous
commit.
Registers coverage gap alert-lifecycle-contract-coverage. Remaining
slices: offline/confirmation families, ack lifecycle, intent
interaction, shadow-mode runtime feed.
rcourtman
7c212b906e