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.Core/Utilities/CollectionPool.cs

@@ -0,0 +1,22 @@
+using Misaki.HighPerformance.Buffer;
+
+namespace Ghost.Core.Utilities;
+
+public class CollectionPool<TCollection, TItem>
+    where TCollection : class, ICollection<TItem>, new()
+{
+    internal static readonly ObjectPool<TCollection> s_pool = new ObjectPool<TCollection>(() => new TCollection(), 1);
+
+    public static TCollection Rent()
+    {
+        return s_pool.Rent();
+    }
+
+    public static void Return(TCollection collection)
+    {
+        collection.Clear();
+        s_pool.Return(collection);
+    }
+}
+
+public class ListPool<T> : CollectionPool<List<T>, T>;