allow to set the recipe already for construction sites

src/lib/sim/BuildingSystem.h

@@ -70,6 +70,18 @@ public:
     // (materials discarded) and reinitializes input buffers (REQ-BLD-SHIPYARD).
     void setShipLayout(BuildingId id, const ShipLayoutConfig& layout);
 
+    // Splitter filter configuration for a queued/under-construction Splitter
+    // site (REQ-BLD-SITE-CONFIG). Operational splitters are configured through
+    // BeltSystem by tile; these mirror that for sites, which are not yet
+    // registered with BeltSystem. getSiteSplitterInfo returns the site's two
+    // output directions (derived from its surface mask) and stored filters, or
+    // nullopt if the id is not a Splitter site. The stored filters are applied
+    // to BeltSystem when the splitter finishes building (tickConstruction).
+    std::optional<BeltSystem::SplitterInfo> getSiteSplitterInfo(BuildingId id) const;
+    void setSiteSplitterFilters(BuildingId id,
+                                const std::vector<ItemType>& filterA,
+                                const std::vector<ItemType>& filterB);
+
     // -- Tick hooks (called from Simulation::tick in the documented order) ---
     void tickConstruction(Tick currentTick);
     void tickBeltPull();