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.Editor.Core/SceneGraph/SceneGraphHelpers.cs

@@ -12,7 +12,7 @@ public class SceneGraphHelpers
     /// <param name="entity">The entity to be wrapped in the <see cref="EntityNode"/>.</param>
     public static EntityNode CreateEntityNode(WorldNode owner, Entity entity, string name)
     {
-        owner.World.EntityManager.AddComponent(entity, LocalToWorld.Identity);
+        owner.World.EntityManager.AddComponent(entity, new LocalToWorld { matrix = Misaki.HighPerformance.Mathematics.float4x4.identity });
         owner.World.EntityManager.AddComponent(entity, Hierarchy.Root);
         return new EntityNode(owner, entity, name);
     }