Inventory live telemetry and state by GridElementType

Artem-requested read-only production/schema audit. Produce specs/active/20260802-composable-entity-detail-pages/entity-now-build-plan/grid-telemetry-inventory.md with per-type GraphQL paths, DB backing tables/columns, measured production population rates, time-series/resolver availability, freshness/connectivity, and Now-exemplar ranking. No config changes or pushes.