ccdc649641
Add KpiRollupAggregation { Gauge, Rate } enum + KpiMetricAggregationCatalog.Resolve(source, metric)
that the hourly rollup fold (T3) consults. Rate = sum-per-hour for per-interval delta counters;
Gauge = last-value-per-hour default (also the safe fallback for unknown/new metrics, never throws).
totalEventsLastHour/errorEventsLastHour classified Gauge (rolling trailing-hour counts, not
per-interval deltas) per authoritative source semantics.
Claude-Session: https://claude.ai/code/session_01MtdgwpEeCUn6cUA5f1LMPj