Refactor material palette system with GPU indirection

Major overhaul of material palette management:
- Added two-buffer indirection (PaletteOffsetBuffer, MaterialIndexBuffer) for GPU material lookup, with incremental upload and resizing.
- MaterialPaletteStore now tracks dirty ranges, supports deferred slot reclamation, and exposes CPU-side arrays for upload.
- ResourceManager manages persistent GPU buffers and uploads only dirty subranges per frame.
- Updated HLSL and C# structs to use palette indices.
- Refactored systems/components to use new palette index and release logic.
- Added RenderContext.UploadBufferRange for partial uploads.
Minor: Fixed StbIApi interop signatures, updated test namespaces, and performed code cleanups.

src/Runtime/Ghost.Engine/Components/GPUInstanceRef.cs

@@ -1,8 +1,11 @@
+using Ghost.Core;
 using Ghost.Entities;
+using Ghost.Graphics.Services;
 
 namespace Ghost.Engine.Components;
 
 public struct GPUInstanceRef : IComponent
 {
-    public uint gpuSceneIndex;
+    public uint gpuInstanceIndex;
+    public Identifier<MaterialPalette> materialPalette;
 }

src/Runtime/Ghost.Engine/RenderPipeline/GhostRenderPipeline.UpdateGPUScene.cs

@@ -27,7 +27,7 @@ internal partial class GhostRenderPipeline
         public float4x4 localToWorld;
         public uint instanceID;
         public uint meshBuffer;
-        public uint materialPalette;
+        public uint materialPaletteIndex;
         public uint renderingLayerMask;
         public uint shadowCastingMode;
     }
@@ -71,7 +71,7 @@ internal partial class GhostRenderPipeline
                     localToWorld = addRequest.localToWorld,
                     instanceID = addRequest.instanceId,
                     meshBuffer = resourceDatabase.GetBindlessIndex(mesh.Get().MeshDataBuffer.AsResource()),
-                    materialPalette = (uint)addRequest.meshInstance.materialPalette.Value,
+                    materialPaletteIndex = (uint)addRequest.meshInstance.materialPalette.Value,
                     renderingLayerMask = addRequest.meshInstance.renderingLayerMask,
                     shadowCastingMode = (uint)addRequest.meshInstance.shadowCastingMode
                 };

src/Runtime/Ghost.Engine/Systems/AddGPUInstanceSystem.cs

@@ -46,7 +46,9 @@ internal class AddGPUInstanceSystem : SystemBase
                 var entity = entities.GetElementUnsafe(i);
 
                 var index = payload.AddInstance(localToWorld.matrix, in meshInstance);
-                systemAPI.World.EntityCommandBuffer.AddComponent(entity, new GPUInstanceRef { gpuSceneIndex = index });
+                var materialPalette = meshInstance.materialPalette;
+
+                systemAPI.World.EntityCommandBuffer.AddComponent(entity, new GPUInstanceRef { gpuInstanceIndex = index, materialPalette = materialPalette });
             }
         }
 

src/Runtime/Ghost.Engine/Systems/RemoveGPUInstanceSystem.cs

@@ -43,7 +43,9 @@ internal class RemoveGPUInstanceSystem : SystemBase
                 var gpuInstance = gpuInstanceRefs.GetElementUnsafe(i);
                 var entity = entities.GetElementUnsafe(i);
 
-                payload.RemoveInstance(gpuInstance.gpuSceneIndex);
+                payload.RemoveInstance(gpuInstance.gpuInstanceIndex);
+                _renderSystem.ResourceManager.ReleaseMaterialPalette(gpuInstance.materialPalette);
+
                 systemAPI.World.EntityCommandBuffer.RemoveComponent<GPUInstanceRef>(entity);
             }
         }

src/Runtime/Ghost.Engine/Systems/UpdateGPUInstanceSystem.cs

@@ -49,7 +49,7 @@ internal class UpdateGPUInstanceSystem : SystemBase
                 ref readonly var mesh = ref meshs.GetElementUnsafe(i);
                 ref readonly var instance = ref gpuInstances.GetElementUnsafe(i);
 
-                playload.UpdateInstance(instance.gpuSceneIndex, ltw.matrix, in mesh);
+                playload.UpdateInstance(instance.gpuInstanceIndex, ltw.matrix, in mesh);
             }
         }
     }