feat(engine): C++ native script system (ScriptBehavior + registry)

ScriptComponent stores only a script name string (POD, serializable);
instances are reconciled by ScriptRuntime each frame (PhysicsWorld
pattern): orphan/rename cleanup with OnDestroy, per-name instantiation
from a file-level self-registering registry (ENGINE_REGISTER_SCRIPT),
OnCreate on bind, OnUpdate after physics step on scaled dt. Engine
framerate loop only sees the base interface, so future Lua/C# behaviors
plug in as foreign ScriptBehavior implementations with zero engine
changes. Ships a Spinner sample script and Inspector script picker.

Engine/src/Serialization/SceneSerializer.cpp

@@ -343,6 +343,14 @@ namespace Engine::Serialization {
                 out << YAML::EndMap;
             }
 
+            // 脚本只存类名（注册表键）；未注册名字加载后运行时警告跳过
+            if (const auto* sc = reg.try_get<ECS::ScriptComponent>(e)) {
+                out << YAML::Key << "Script" << YAML::Value << YAML::BeginMap;
+                out << YAML::Key << "ScriptName" << YAML::Value
+                    << sc->scriptName;
+                out << YAML::EndMap;
+            }
+
             out << YAML::EndMap;   // Components
             out << YAML::EndMap;   // Entity
         }
@@ -628,6 +636,12 @@ namespace Engine::Serialization {
                 cc.stepHeight = n["StepHeight"].as<f32>(cc.stepHeight);
                 // 状态（速度/着地）由 PhysicsWorld 对账重建，不存
             }
+
+            // 脚本：只存类名；未注册名字由 ScriptRuntime 运行时警告跳过
+            if (const YAML::Node n = comps["Script"]) {
+                auto& sc = handle.AddComponent<ECS::ScriptComponent>();
+                sc.scriptName = n["ScriptName"].as<std::string>("");
+            }
         }
 
         // 加载在 OnImGuiRender 段，错过本帧 UpdateTransforms：