Return the user-explicit override for key without falling back to
the schema default. undefined when nothing has been
setSetting'd — even when the schema declares a default. Lets
consumers distinguish "user explicitly set this" from "schema
default is in effect" for chain-resolution flows (e.g.,
LocomotionApi.defaultModeFor defers to the bodyplan default
only when there's no explicit override).
Public shape provided by
EnvironmentMixin— methods only, per the inter-stuff contract. ThepersistentStore(Hydrator-saved) andsessionStore(transient) stores live as public fields on the implementing class so the Hydrator can reflect into them by name, but they are NOT part of the contract surface; external code goes throughgetSetting/setSetting/setVar/listVars. Tests that need raw state reach for the concrete class type, not theEnvironmentnarrowing.