Player-facing commands that operate on this mixin's stores.
Picked up by CommandGiver discovery via the self slot.
Persistent fields declared by this mixin. The Hydrator uses
this list; persistentStore is a plain Record so it
round-trips through Mongo without a custom handler.
Shell-tier settings the substrate owns. The substrate
historically declared none (D6); shell.interpolate-vars
lives here because it gates a substrate-wide behavior that
keys off EnvironmentMixin's presence — declaring it
elsewhere would split the contract.
EnvironmentMixin factory. The class form is
@Unshadowableonly on the privacy-gated methods (setSetting,unsetSetting); other methods remain shadowable for tracing / extension.