Render graph: native pass merging & heap-based aliasing

Major architecture upgrade:
- Add native render pass merging (hardware pass grouping, load/store op inference)
- Implement heap-based aliasing for textures & buffers (D3D12-style)
- Unify resource model: buffers and textures in one registry
- Extend builder API for buffer creation/usage, access flags, hints
- Improve barrier/state tracking (buffer hints, indirect argument state)
- Update caching, hashing, and debug output for new model
- Add enums/structs: AttachmentLoadOp, StoreOp, BufferHint, etc.
- D3D12 backend: support named resources, temp upload buffers, correct heap usage
- Update docs, benchmarks, and project files for new features

Brings render graph closer to AAA engine standards, enabling efficient memory usage, lower driver overhead, and a more flexible API.

Ghost.Graphics/D3D12/D3D12Renderer.cs

@@ -95,6 +95,8 @@ internal class D3D12Renderer : IRenderer
             {
                 Texture = target,
                 ClearColor = clearColor,
+                LoadOp = AttachmentLoadOp.Clear,
+                StoreOp = AttachmentStoreOp.Store,
             },
         ];
 
@@ -103,6 +105,10 @@ internal class D3D12Renderer : IRenderer
             Texture = Handle<Texture>.Invalid,
             ClearDepth = 1.0f,
             ClearStencil = 0,
+            DepthLoadOp = AttachmentLoadOp.Clear,
+            StencilLoadOp = AttachmentLoadOp.Clear,
+            DepthStoreOp = AttachmentStoreOp.Store,
+            StencilStoreOp = AttachmentStoreOp.Store,
         };
 
         // NOTE: Testing only.