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.Graphics/Contracts/IShaderCompiler.cs

@@ -39,6 +39,7 @@ public ref struct ShaderCompilationConfig
     public ReadOnlySpan<string> includes;
     public string shaderPath;
     public string entryPoint;
+    public string? injectedCode;
     public ShaderStage stage;
     public CompilerTier tier;
     public CompilerOptimizeLevel optimizeLevel;