Zero-based index of this zone within the flat zones array.
Every location in the body, each paired with its flat locations index.
The Logic that owns the entity. Required (the constructor throws without it) and transient — held in memory, never written to JSON.
This zone's parts, each paired with its flat parts index.
The first zone number allocated to this zone.
Owning body structure (supplies actor and body-owner logic).
Construction options for a BodyZone instance.