subscribeTo

Subscribe this aggregate's data to a higher-level aggregate r — i.e., make r observe (roll up) every line item this aggregate exposes. Data flows this → r.

Direction note (regression-fixed): the original implementation had this reversed (this.observe(r)), which silently starved the higher-level aggregate of all observations and made network-level inventory aggregates report 0 / NaN. The convention now matches ksl.modeling.supplychain.inventory.Inventory.attachAggregateInventoryResponse, which also writes r.aggregateXxx.observe(myXxx).