PARKED: Event Ceiling/Reserved KPIs — event-start commitment snapshots (recon Part B Phase 2)

Parked on 2026-06-12 per Richie. The perfection-vs-performance KPI model needs event-start snapshots of (a) per-device capacity ceiling and (b) reserved/withheld capacity. BatteryStaticState.capacity and BatteryState.backupReserve exist but are live telemetry — NOT snapshotted at dispatch. LeapGroupDispatch.nomination_kw exists but per-device mapping unclear. No derate records anywhere. This is the bigger lift: new domain table for per-event commitment snapshots, dispatch-time writer, KPI compute on top. Design pass needed before scoping. Recon doc: recon/2026-06-12-event-metrics-kpi.md (Part B). NO Linear ticket yet — file when Richie is ready to design.