feat(render): refactor pipeline & shader system for DX12 WG

Major refactor of render pipeline and shader system:
- Replaced legacy shader properties with source generator and attribute-based HLSL struct generation.
- Introduced ShaderPropertiesRegistry for runtime property layout/code registration.
- Added modular IRenderPipeline, IRenderPipelineSettings, and IRenderPayload interfaces.
- Implemented GhostRenderPipeline and ECS-driven GPUScene management.
- Added experimental DirectX 12 Work Graph support.
- Refactored shader compilation, variant hashing, and caching.
- Updated APIs for consistency and improved codegen for registration.

These changes modernize the rendering infrastructure for advanced features like work graphs and dynamic pipelines.

BREAKING CHANGE: Shader DSL, pipeline, and property APIs have changed. Existing shaders and pipeline integrations must be updated.

src/Runtime/Ghost.Core/Handle.cs

@@ -186,6 +186,9 @@ public readonly struct Key64<T> : IEquatable<Key64<T>>
     {
         return !a.Equals(b);
     }
+
+    public static implicit operator ulong(Key64<T> key) => key.Value;
+    public static implicit operator Key64<T>(ulong value) => new Key64<T>(value);
 }
 
 public readonly struct Key128<T> : IEquatable<Key128<T>>
@@ -239,4 +242,7 @@ public readonly struct Key128<T> : IEquatable<Key128<T>>
     {
         return !a.Equals(b);
     }
+
+    public static implicit operator UInt128(Key128<T> key) => key.Value;
+    public static implicit operator Key128<T>(UInt128 value) => new Key128<T>(value);
 }