Add high-performance material/shader system (Ghost.Shader.Concept)

Introduces a new Ghost.Shader.Concept project implementing a modern, data-oriented material and shader system with:
- Global/local keyword bitsets (fast O(1) ops, 64 bytes)
- Multi-pass shader program and per-pass render state overrides
- Thread-safe, 16-byte aligned material property blocks
- Material pooling to reduce GC pressure
- Batch renderer for efficient PSO grouping and async variant warmup
- Full demo (Program.cs) and extensive documentation (ARCHITECTURE.md, README.md, PROJECT_SUMMARY.md)
- Minor integration: new enums, doc updates, and keyword handling in existing code

No breaking changes to the existing engine; all new code is isolated. This serves as a reference implementation for high-performance, extensible material/shader architectures.

Ghost.Core/Contracts/ICloneable.cs

@@ -0,0 +1,11 @@
+namespace Ghost.Core.Contracts;
+
+public interface ICloneable
+{
+    object Clone();
+}
+
+public interface ICloneable<T>
+{
+    T Clone();
+}

Ghost.Core/Graphics/PipelineState.cs

@@ -1,6 +1,6 @@
 namespace Ghost.Core.Graphics;
 
-public enum ZTest
+public enum ZTest : byte
 {
     Disabled,
     Less,
@@ -12,20 +12,20 @@ public enum ZTest
     Always
 }
 
-public enum ZWrite
+public enum ZWrite : byte
 {
     Off,
     On
 }
 
-public enum Cull
+public enum Cull : byte
 {
     Off,
     Front,
     Back
 }
 
-public enum Blend
+public enum Blend : byte
 {
     Opaque,
     Alpha,
@@ -35,7 +35,7 @@ public enum Blend
 }
 
 [Flags]
-public enum ColorWriteMask
+public enum ColorWriteMask : byte
 {
     None = 0,
     Red = 1 << 0,

Ghost.Core/Graphics/ShaderDescriptor.cs

@@ -1,9 +1,9 @@
 namespace Ghost.Core.Graphics;
 
-public enum KeywordType
+public enum KeywordSpace
 {
-    Static,
-    Dynamic,
+    Local,
+    Global,
 }
 
 public enum ShaderPropertyType
@@ -29,7 +29,7 @@ public struct ShaderEntryPoint
 
 public struct KeywordsGroup
 {
-    public KeywordType type;
+    public KeywordSpace space;
     public List<string>? keywords;
 }
 

Ghost.Core/TypeHandle.cs

@@ -15,18 +15,18 @@ public readonly struct TypeHandle
     }
 
     /// <summary>
-    /// Gets the type handle for the specified type.
+    /// Gets the space handle for the specified space.
     /// </summary>
-    /// <param name="type">The type to get the handle for.</param>
-    /// <returns>The type handle as a nint.</returns>
+    /// <param name="type">The space to get the handle for.</param>
+    /// <returns>The space handle as a nint.</returns>
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public static TypeHandle Get(Type type) => new TypeHandle(type.TypeHandle.Value);
 
     /// <summary>
-    /// Gets the type handle for the specified type.
+    /// Gets the space handle for the specified space.
     /// </summary>
-    /// <typeparam name="T">The type to get the handle for.</typeparam>
-    /// <returns>The type handle as a nint.</returns>
+    /// <typeparam name="T">The space to get the handle for.</typeparam>
+    /// <returns>The space handle as a nint.</returns>
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public static TypeHandle Get<T>() => Get(typeof(T));