fix belts were not drawn

src/lib/sim/BuildingSystem.cpp

@@ -656,6 +656,21 @@ std::vector<ConstructionSite> BuildingSystem::allSites() const
                                          m_constructionQueue.end());
 }
 
+std::vector<BuildingSystem::BeltTileInfo> BuildingSystem::allBeltTiles() const
+{
+    std::vector<BeltTileInfo> result;
+    result.reserve(m_beltEntities.size());
+    for (const std::map<EntityId, BeltEntry>::value_type& kv : m_beltEntities)
+    {
+        BeltTileInfo info;
+        info.id   = kv.first;
+        info.tile = kv.second.tile;
+        info.type = kv.second.type;
+        result.push_back(info);
+    }
+    return result;
+}
+
 bool BuildingSystem::isTileOccupied(QPoint tile) const
 {
     return m_tileOccupancy.count({tile.x(), tile.y()}) > 0;

src/lib/sim/BuildingSystem.h

@@ -55,10 +55,18 @@ public:
     void tickBeltPush();
 
     // -- Queries -------------------------------------------------------------
+    struct BeltTileInfo
+    {
+        EntityId     id;
+        QPoint       tile;
+        BuildingType type;  // Belt or Splitter
+    };
+
     const Building*           findBuilding(EntityId id)  const;
     const ConstructionSite*   findSite(EntityId id)      const;
     std::vector<Building>     allBuildings()             const;
     std::vector<ConstructionSite> allSites()             const;
+    std::vector<BeltTileInfo> allBeltTiles()             const;
     bool                      isTileOccupied(QPoint tile) const;
 
     // Find nearest operational building of the given type; nullptr if none.