Implement clientless transports, Lua reload and same-map portals

Add native transport recording and execution with grid lifecycle handling, clientless teleport acknowledgements, and regression tests. Support targeted same-map portal imports and preserve disabled taxi nodes. Document live transport and portal verification and the remaining portal inventory.

src/server/game/Maps/MapManager.cpp

@@ -74,6 +74,8 @@ Map* MapManager::CreateWorldMap(uint32 mapId, uint32 instanceId)
     map->LoadRespawnTimes();
     map->LoadCorpseData();
 
+    map->LoadTransportGameObjectGrids();
+
     if (sWorld->getBoolConfig(CONFIG_BASEMAP_LOAD_GRIDS))
         map->LoadAllCells();
 
@@ -104,6 +106,8 @@ InstanceMap* MapManager::CreateInstance(uint32 mapId, uint32 instanceId, Instanc
     bool load_data = save != nullptr;
     map->CreateInstanceData(load_data);
 
+    map->LoadTransportGameObjectGrids();
+
     if (sWorld->getBoolConfig(CONFIG_INSTANCEMAP_LOAD_GRIDS))
         map->LoadAllCells();
 
@@ -118,6 +122,7 @@ BattlegroundMap* MapManager::CreateBattleground(uint32 mapId, uint32 instanceId,
     ASSERT(map->IsBattlegroundOrArena());
     map->SetBG(bg);
     bg->SetBgMap(map);
+    map->LoadTransportGameObjectGrids();
     return map;
 }