feat: scene ghosting, as the client streams a zone's scenes

The client keeps the scene under the player loaded, the scenes the zone
file's transitions connect to it, and the global scene
(Zone::StreamScenesAroundPosition 0x0108a3f0, TerrainManager::GetSceneAtPos
0x01069010, the connected scenes at 0x01066500; transitions naming a
missing scene dropped as Zone::FixupInvalidTransitions 0x010842e0 does).

- ZoneScenes (dCommon): the terrain's scene map lookup and the scene graph,
  shared by the world server and the dashboard.
- Objects remember the scene they were placed in (spawners pass theirs on).
- ghosting_scenes=1 (world config, off by default): players get the objects
  of their loaded scenes instead of the ones within the ghosting distances;
  objects from no scene go by the scene under them. Zones without a scene
  map keep distance ghosting.

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

dGame/EntityManager.h

@@ -62,6 +62,7 @@ public:
 	void CheckGhosting(Entity* entity);
 	Entity* GetGhostCandidate(LWOOBJID id) const;
 	bool GetGhostingEnabled() const;
+	bool GetSceneGhosting() const { return m_SceneGhosting; }
 
 	void ScheduleForKill(Entity* entity);
 
@@ -109,6 +110,9 @@ private:
 	float m_GhostDistanceMinSqaured = 100 * 100;
 	float m_GhostDistanceMaxSquared = 150 * 150;
 	bool m_GhostingEnabled = true;
+	// ghosting_scenes: players get the objects of the scenes their client keeps loaded (ZoneScenes) instead of the
+	// ones within the ghosting distances
+	bool m_SceneGhosting = false;
 
 	std::stack<uint16_t> m_LostNetworkIds;