Boss gate: a boss zone spawns its faction's boss, and RunGoal derives whether the exit gate is open

EntityPack.Boss (key 21) carries Entity.IsBoss through save and Continue. GenerateZone adds one boss
per BossZones entry before the ambient return, flying the faction's BossHull or, with the gap logged,
its most expensive available ship hull. RunGoal (ServerShared) is the one owner of boss life and exit
state, derived from Zone.Entities.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Assets/Scripts/ServerShared/Entity.cs

@@ -16,6 +16,8 @@ public abstract class Entity
 {
     public Zone Zone;
     public Faction Faction;
+    // The mark of a zone's boss, written only by ZoneGenerator and restored from the pack. RunGoal reads it.
+    public bool IsBoss;
     public EquippableItem Hull;
     public EquippedItem EquippedHull;