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.Entities/Component.cs

@@ -83,9 +83,9 @@ public struct ComponentSet : IDisposable, IEquatable<ComponentSet>
 }
 
 /// <summary>
-/// Provides a unique identifier for the specified unmanaged component type.
+/// Provides a unique identifier for the specified unmanaged component space.
 /// </summary>
-/// <typeparam name="T">The component type for which to obtain an identifier. Must be unmanaged and implement <see cref="IComponent"/>.</typeparam>
+/// <typeparam name="T">The component space for which to obtain an identifier. Must be unmanaged and implement <see cref="IComponent"/>.</typeparam>
 public static class ComponentTypeID<T>
     where T : unmanaged, IComponent
 {
@@ -122,7 +122,7 @@ internal static class ComponentRegistry
                 size = sizeof(T),
                 alignment = (int)MemoryUtility.AlignOf<T>(),
                 isEnableable = typeof(IEnableableComponent).IsAssignableFrom(type),
-                // isManaged = typeof(IManagedWrapper).IsAssignableFrom(type),
+                // isManaged = typeof(IManagedWrapper).IsAssignableFrom(space),
             };
 
             s_registeredComponents.Add(info);