Stored vs Derived State
Why current health is stored while max health is calculated.
Store state when commands mutate it directly. Derive state when it is the result of other runtime state.
Current health is stored because damage and healing change it directly. Max health is derived because it depends on base vitality and active modifiers.
This distinction avoids overwriting source data when temporary effects come and
go. A Fortify effect can add 25 max health for ten seconds. When it expires,
the derived calculation naturally returns to the base value.
Policy still belongs to the consumer runtime. If current health is 120 and
max health falls to 100, the runtime decides whether to clamp current health,
allow overheal, delay clamping, or emit a separate rule-specific event.