feat: add runtime play tick and play-mode scene editing semantics

engine/include/XCEngine/Scene/RuntimeLoop.h

@@ -0,0 +1,45 @@
+#pragma once
+
+#include <XCEngine/Scene/SceneRuntime.h>
+
+#include <cstdint>
+
+namespace XCEngine {
+namespace Components {
+
+class RuntimeLoop {
+public:
+    struct Settings {
+        float fixedDeltaTime = 1.0f / 50.0f;
+        float maxFrameDeltaTime = 0.1f;
+        uint32_t maxFixedStepsPerFrame = 4;
+    };
+
+    explicit RuntimeLoop(Settings settings = {});
+
+    void SetSettings(const Settings& settings);
+    const Settings& GetSettings() const { return m_settings; }
+
+    void Start(Scene* scene);
+    void Stop();
+
+    void Tick(float deltaTime);
+    void Pause();
+    void Resume();
+    void StepFrame();
+
+    bool IsRunning() const { return m_sceneRuntime.IsRunning(); }
+    bool IsPaused() const { return m_paused; }
+    Scene* GetScene() const { return m_sceneRuntime.GetScene(); }
+    float GetFixedAccumulator() const { return m_fixedAccumulator; }
+
+private:
+    SceneRuntime m_sceneRuntime;
+    Settings m_settings = {};
+    float m_fixedAccumulator = 0.0f;
+    bool m_paused = false;
+    bool m_stepRequested = false;
+};
+
+} // namespace Components
+} // namespace XCEngine