Refactor pipeline state and render output abstractions

- Replace old pipeline enums/structs with new strongly-typed PipelineState and enums (ZTest, ZWrite, Cull, Blend, ColorWriteMask)
- Redesign pipeline keying: introduce 128-bit GraphicsPipelineKey, MaterialPipelineKey, and PassPipelineKey for robust PSO caching
- Replace IRenderTargetStrategy with IRenderOutput; add SwapChainRenderOutput and TextureRenderOutput
- Update renderer and window code to use new render output abstraction and handle viewport/scissor updates
- Make ShaderPass a readonly struct and Shader a struct; use ID-based pass lookup for efficiency
- Materials now support per-pass pipeline overrides with new keying
- Add defensive checks in D3D12CommandBuffer; update D3D12PipelineLibrary for new keying/state
- Move test shader to test.gsdef and update for new pipeline state syntax
- Remove obsolete files/interfaces and perform general code cleanups
- Update all usages and parsing logic for new pipeline state system

Ghost.Core/Graphics/ShaderDescriptor.cs

@@ -33,24 +33,6 @@ public struct KeywordsGroup
     public List<string>? keywords;
 }
 
-public struct PipelineDescriptor
-{
-    public ZTestOptions zTest;
-    public ZWriteOptions zWrite;
-    public CullOptions cull;
-    public BlendOptions blend;
-    public uint colorMask;
-
-    public static PipelineDescriptor Default = new PipelineDescriptor
-    {
-        zTest = ZTestOptions.LessEqual,
-        zWrite = ZWriteOptions.On,
-        cull = CullOptions.Back,
-        blend = BlendOptions.Opaque,
-        colorMask = 0
-    };
-}
-
 public interface IPassDescriptor
 {
     public string Identifier
@@ -81,7 +63,7 @@ public class FullPassDescriptor : IPassDescriptor
     public ShaderEntryPoint pixelShader;
     public List<string>? defines;
     public List<KeywordsGroup>? keywords;
-    public PipelineDescriptor localPipeline;
+    public PipelineState localPipeline;
 
     public string Identifier => uniqueIdentifier;
     public string Name => name;