Refactor render pipeline and resource management APIs

Split IFenceSynchronizer/IRenderSystem interfaces for clarity. Refactor D3D12GraphicsEngine to use IFenceSynchronizer. Update RenderGraph and context to use explicit resource manager/database/allocator references. Add multi-buffering methods to IRGBuilder (stub). Support history access for multi-frame resources. Remove legacy RenderPipelineBase; introduce IRenderPipelineSettings and sealed GhostRenderPipeline. Clean up resource aliasing and pool logic. Improve modularity and future extensibility.

src/Runtime/Ghost.Graphics.RHI/IFenceSynchronizer.cs

@@ -28,20 +28,3 @@ public interface IFenceSynchronizer
     void SignalCPUReady();
     void WaitIdle();
 }
-
-public interface IRenderSystem : IFenceSynchronizer, IDisposable
-{
-    IGraphicsEngine GraphicsEngine
-    {
-        get;
-    }
-
-    bool IsRunning
-    {
-        get;
-    }
-
-    void Start();
-    void Stop();
-    void RequestSwapChainResize(ISwapChain swapChain, uint2 newSize);
-}