Refactor render graph & DSL; remove material system

- Major optimization of Ghost.RenderGraph.Concept: pooled resources, zero-allocation hot paths, explicit queue types, and batch barrier APIs.
- Migrated Ghost.DSL shader compiler to ANTLR4-based parser; removed hand-written parser, added grammar files and semantic model conversion.
- Added CollectionPool/ListPool for pooled list management.
- Updated documentation for new architecture and performance.
- Removed Ghost.Shader.Concept (material/material system) from repo and solution.
- README.md replaced with a brief project statement.

Ghost.Entities.Test/SerializationTest.cs

@@ -40,9 +40,9 @@ public class SerializationTest : ITest
         writer.WriteString("Name", "world 1");
         writer.WriteStartArray("Entities");
 
-        for (var i = 0; i < _world.ArchetypeCount; i++)
+        for (var i = 0; i < _world.ComponentManager.ArchetypeCount; i++)
         {
-            ref var archetype = ref _world.GetArchetypeReference(i);
+            ref var archetype = ref _world.ComponentManager.GetArchetypeReference(i);
 
             for (var j = 0; j < archetype.ChunkCount; j++)
             {