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/RenderPipeline/IRenderPipeline.cs

@@ -0,0 +1,14 @@
+using Ghost.Graphics.Core;
+using Ghost.Graphics.RHI;
+
+namespace Ghost.Graphics.RenderPipeline;
+
+public interface IRenderPipelineSettings
+{
+    static abstract IRenderPipeline CreatePipeline(IRenderSystem renderSystem);
+}
+
+public interface IRenderPipeline : IDisposable
+{
+    void Render(RenderContext ctx, ReadOnlySpan<RenderRequest> requests);
+}