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.RenderGraph.Concept/ConsoleAPI.cs

@@ -0,0 +1,16 @@
+namespace Ghost.RenderGraph.Concept;
+
+internal static class ConsoleAPI
+{
+    [System.Diagnostics.Conditional("DEBUG")]
+    public static void WriteLine()
+    {
+        Console.WriteLine();
+    }
+
+    [System.Diagnostics.Conditional("DEBUG")]
+    public static void WriteLine(string? message)
+    {
+        Console.WriteLine(message);
+    }
+}