Refactor render graph: modular compilation & execution

Major overhaul of render graph system for modularity and performance:
- Split compilation and execution logic into dedicated classes (Compiler, Executor, NativePassBuilder, Barriers)
- Overhauled barrier system: now uses CompiledBarrier with target state only, querying before state at execution
- Resource size/alignment now queried from D3D12 device for accurate heap allocation
- ResourceDesc now includes Type field and asserts correct union access
- Centralized D3D12 interop logic in D3D12Utility extensions
- Added RenderGraphHasher for structural graph hashing and cache invalidation
- RenderGraph class simplified to orchestrate specialized components
- ResourceAliasingManager now uses allocator for size queries
- Compilation cache now stores compiled barriers, reducing memory usage
- Improved comments, debug assertions, and removed redundant code

Result: more maintainable, efficient, and robust render graph pipeline.

Ghost.Graphics/D3D12/Utilities/D3D12Utility.cs

@@ -7,7 +7,7 @@ using static TerraFX.Aliases.DXGI_Alias;
 
 namespace Ghost.Graphics.D3D12.Utilities;
 
-internal unsafe static class D3D12Utility
+internal static unsafe class D3D12Utility
 {
     public static void SetName<T>(ref this T obj, ReadOnlySpan<char> name)
         where T : unmanaged, ID3D12Object.Interface
@@ -278,6 +278,102 @@ internal unsafe static class D3D12Utility
         };
     }
 
+    public static D3D12_RESOURCE_FLAGS ToD3D12ResourceFlag(this TextureUsage usage)
+    {
+        var flags = D3D12_RESOURCE_FLAG_NONE;
+
+        if (usage.HasFlag(TextureUsage.RenderTarget))
+        {
+            flags |= D3D12_RESOURCE_FLAG_ALLOW_RENDER_TARGET;
+        }
+
+        if (usage.HasFlag(TextureUsage.DepthStencil))
+        {
+            flags |= D3D12_RESOURCE_FLAG_ALLOW_DEPTH_STENCIL;
+        }
+
+        if (usage.HasFlag(TextureUsage.UnorderedAccess))
+        {
+            flags |= D3D12_RESOURCE_FLAG_ALLOW_UNORDERED_ACCESS;
+        }
+
+        return flags;
+    }
+
+    public static D3D12_RESOURCE_DESC ToD3D12ResourceDesc(this in TextureDesc desc)
+    {
+        var dxgiFormat = desc.Format.ToDXGIFormat();
+        var maxDimension = Math.Max(desc.Width, Math.Max(desc.Height, desc.Slice));
+        var mipLevels = desc.MipLevels == 0
+            ? (ushort)(1 + Math.Floor(Math.Log2(maxDimension)))
+            : (ushort)desc.MipLevels;
+
+        var resourceFlags = desc.Usage.ToD3D12ResourceFlag();
+        return desc.Dimension switch
+        {
+            TextureDimension.Texture2D => D3D12_RESOURCE_DESC.Tex2D(
+                                dxgiFormat,
+                                desc.Width,
+                                desc.Height,
+                                mipLevels: mipLevels,
+                                flags: resourceFlags),
+            TextureDimension.Texture3D => D3D12_RESOURCE_DESC.Tex3D(
+                                dxgiFormat,
+                                desc.Width,
+                                desc.Height,
+                                (ushort)desc.Slice,
+                                flags: resourceFlags),
+            TextureDimension.TextureCube => D3D12_RESOURCE_DESC.Tex2D(
+                                dxgiFormat,
+                                desc.Width,
+                                desc.Height,
+                                mipLevels: mipLevels,
+                                arraySize: 6,
+                                flags: resourceFlags),
+            TextureDimension.Texture2DArray => D3D12_RESOURCE_DESC.Tex2D(
+                                dxgiFormat,
+                                desc.Width,
+                                desc.Height,
+                                mipLevels: mipLevels,
+                                arraySize: (ushort)desc.Slice,
+                                flags: resourceFlags),
+            TextureDimension.TextureCubeArray => D3D12_RESOURCE_DESC.Tex2D(
+                                dxgiFormat,
+                                desc.Width,
+                                desc.Height,
+                                mipLevels: mipLevels,
+                                arraySize: (ushort)(desc.Slice * 6),
+                                flags: resourceFlags),
+            _ => throw new ArgumentException($"Unsupported texture dimension: {desc.Dimension}"),
+        };
+    }
+
+    public static D3D12_RESOURCE_FLAGS ToD3D12ResourceFlag(this BufferUsage usage)
+    {
+        var flags = D3D12_RESOURCE_FLAG_NONE;
+
+        if (usage.HasFlag(BufferUsage.Raw) || usage.HasFlag(BufferUsage.UnorderedAccess))
+        {
+            flags |= D3D12_RESOURCE_FLAG_ALLOW_UNORDERED_ACCESS;
+        }
+
+        return flags;
+    }
+
+    public static D3D12_RESOURCE_DESC ToD3D12ResourceDesc(this in BufferDesc desc)
+    {
+        var alignedSize = desc.Size;
+        if (desc.Usage.HasFlag(BufferUsage.Constant))
+        {
+            // D3D12 CBV size must be 256-byte aligned
+            alignedSize = (uint)(desc.Size + 255) & ~255u;
+        }
+
+        var resourceFlags = desc.Usage.ToD3D12ResourceFlag();
+        return D3D12_RESOURCE_DESC.Buffer(alignedSize, resourceFlags);
+    }
+
+
     public static ResourceDesc ToResourceDesc(this D3D12_RESOURCE_DESC desc)
     {
         if (desc.Dimension == D3D12_RESOURCE_DIMENSION.D3D12_RESOURCE_DIMENSION_BUFFER)