Refactor error handling: use Error enum, update APIs

Replaces ErrorStatus with Error across all systems for consistency.
Renames ResourceBarrierData fields to camelCase.
Adds BindlessAccess enum and updates GetBindlessIndex API.
Updates method signatures, result types, and error checks.
Modernizes HLSL mesh shader syntax and fixes naming.
Improves code style and updates comments for clarity.

Ghost.Graphics/D3D12/D3D12SwapChain.cs

@@ -159,9 +159,9 @@ internal unsafe class D3D12SwapChain : ISwapChain
 
             var barrierData = new ResourceBarrierData
             {
-                Access = BarrierAccess.NoAccess,
-                Layout = BarrierLayout.Present,
-                Sync = BarrierSync.None,
+                access = BarrierAccess.NoAccess,
+                layout = BarrierLayout.Present,
+                sync = BarrierSync.None,
             };
 
             var handle = _resourceDatabase.ImportExternalResource(pBackBuffer, barrierData, view);