Shared accumulation logic for modifications (active effects + features).
This module consolidates the field-family stacking rules and operation handling
used by both _applyModifications (actor prepareDerivedData) and
getEffectiveModifierValue (mid-resolution queries).
Shared accumulation logic for modifications (active effects + features). This module consolidates the field-family stacking rules and operation handling used by both _applyModifications (actor prepareDerivedData) and getEffectiveModifierValue (mid-resolution queries).