snapshot Cost Observables
Capture an InventoryCostObservables snapshot of this inventory's current within-replication state. Intended to be called from a cost calculator's ModelElementObserver.replicationEnded(this) callback, when KSL guarantees the within-replication statistics are stable for the post-warmup window.
Capture a BuilderCostObservables snapshot from this builder. Loops over DemandLoadBuilder.trackedItemTypes and reads each item's TW-average units-on-hand; returns an empty per-item map when the builder was constructed without an itemTypes list.