switch to ECS architecture

src/lib/sim/ScrapSystem.h

@@ -1,28 +1,37 @@
 #pragma once
 
-#include <functional>
 #include <optional>
 #include <vector>
 
 #include <QVector2D>
 
-#include "EntityId.h"
-#include "Scrap.h"
+#include "EcsComponents.h"
 #include "Tick.h"
 
+#include "entt/entity/entity.hpp"
+
+class EntityAdmin;
+
+struct ScrapInfo
+{
+    entt::entity entity;
+    QVector2D position;
+};
+
 class ScrapSystem
 {
 public:
-    explicit ScrapSystem(std::function<EntityId()> allocateId);
+    explicit ScrapSystem(EntityAdmin& admin);
 
-    EntityId             spawn(QVector2D position, int amount, Tick despawnAt);
-    void                 tickDespawn(Tick currentTick);
-    std::optional<Scrap> consume(EntityId id);  // removes and returns scrap, or nullopt
+    entt::entity spawn(QVector2D position, int amount, Tick despawnAt);
+    void         tickDespawn(Tick currentTick);
 
-    const Scrap*       findScrap(EntityId id) const;
-    std::vector<Scrap> allScraps()            const;
+    // Removes the scrap and returns its amount, or nullopt if not found.
+    std::optional<int> consume(entt::entity entity);
+
+    // Lightweight snapshot for callers that need to iterate all scrap.
+    std::vector<ScrapInfo> allScrapInfo() const;
 
 private:
-    std::function<EntityId()> m_allocateId;
-    std::vector<Scrap>        m_scraps;
+    EntityAdmin& m_admin;
 };