explicit recipe unlocking

src/lib/config/ConfigLoader.cpp

@@ -367,6 +367,15 @@ RecipesConfig ConfigLoader::loadRecipes(const std::string& path)
         }
         def.building = *parsedType;
 
+        if (def.building == BuildingType::Assembler)
+        {
+            const auto level = mt["unlock_at_station_level"].value<int64_t>();
+            if (level)
+            {
+                def.unlockAtStationLevel = static_cast<int>(*level);
+            }
+        }
+
         // inputs may be omitted (e.g. miner recipes). An empty array is fine.
         if (mt.contains("inputs"))
         {

src/lib/config/RecipesConfig.h

@@ -32,6 +32,10 @@ struct RecipeDef
     std::vector<RecipeIngredient> inputs;
     std::vector<RecipeOutput> outputs;
     double durationSeconds;
+    // Assembler only. nullopt = implicit-only locking. -1 = explicitly unlocked
+    // at game start. >= 0 = locked; schematic enters drop pool at that station
+    // level once the output item is implicitly unlocked (REQ-LOCK-EXPLICIT).
+    std::optional<int> unlockAtStationLevel;
 };
 
 struct RecipesConfig