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.DSL/Grammar/GhostShaderLexer.g4

@@ -0,0 +1,33 @@
+lexer grammar GhostShaderLexer;
+
+// Keywords
+SHADER: 'shader';
+PROPERTIES: 'properties';
+PIPELINE: 'pipeline';
+PASS: 'pass';
+DEFINES: 'defines';
+KEYWORDS: 'keywords';
+INCLUDES: 'includes';
+GLOBAL: 'global';
+LOCAL: 'local';
+HLSL: 'hlsl';
+
+// Punctuation
+LBRACE: '{';
+RBRACE: '}';
+LPAREN: '(';
+RPAREN: ')';
+SEMICOLON: ';';
+COMMA: ',';
+EQUALS: '=';
+COLON: ':';
+
+// Literals
+STRING_LITERAL: '"' (~["\r\n] | '\\' .)* '"';
+NUMBER: [0-9]+ ('.' [0-9]+)? | '.' [0-9]+;
+IDENTIFIER: [a-zA-Z_][a-zA-Z0-9_]*;
+
+// Whitespace and Comments
+WS: [ \t\r\n]+ -> skip;
+LINE_COMMENT: '//' ~[\r\n]* -> skip;
+BLOCK_COMMENT: '/*' .*? '*/' -> skip;

Ghost.DSL/Grammar/GhostShaderParser.g4

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+parser grammar GhostShaderParser;
+
+options {
+    tokenVocab = GhostShaderLexer;
+}
+
+// Top-level rule
+shaderFile: shader+ EOF;
+
+shader:
+    SHADER STRING_LITERAL LBRACE
+        shaderBody
+    RBRACE;
+
+shaderBody:
+    (propertiesBlock | pipelineBlock | passBlock | functionCall)*;
+
+// Properties block
+propertiesBlock:
+    PROPERTIES LBRACE
+        propertyDeclaration*
+    RBRACE;
+
+propertyDeclaration:
+    scope? IDENTIFIER IDENTIFIER (EQUALS LBRACE propertyInitializer RBRACE)? SEMICOLON;
+
+scope:
+    GLOBAL | LOCAL;
+
+propertyInitializer:
+    (NUMBER | IDENTIFIER) (COMMA (NUMBER | IDENTIFIER))*;
+
+// Pipeline block
+pipelineBlock:
+    PIPELINE LBRACE
+        pipelineStatement*
+    RBRACE;
+
+pipelineStatement:
+    IDENTIFIER EQUALS IDENTIFIER SEMICOLON;
+
+// Pass block
+passBlock:
+    PASS STRING_LITERAL LBRACE
+        passBody
+    RBRACE;
+
+// Template
+passBody:
+    (definesBlock | includesBlock | keywordsBlock | pipelineBlock | hlslBlock | shaderEntry)*;
+
+definesBlock:
+    DEFINES LBRACE
+        defineStatement*
+    RBRACE;
+
+defineStatement:
+    IDENTIFIER SEMICOLON;
+
+includesBlock:
+    INCLUDES LBRACE
+        includeStatement*
+    RBRACE;
+
+includeStatement:
+    STRING_LITERAL SEMICOLON;
+
+keywordsBlock:
+    KEYWORDS LBRACE
+        keywordStatement*
+    RBRACE;
+
+keywordStatement:
+    scope? IDENTIFIER (COMMA IDENTIFIER)* SEMICOLON;
+
+hlslBlock:
+    HLSL LBRACE
+        hlslCode
+    RBRACE;
+
+hlslCode:
+    .*? ;  // Capture everything inside hlsl block
+
+shaderEntry:
+    IDENTIFIER STRING_LITERAL COLON STRING_LITERAL SEMICOLON;
+
+functionCall:
+    IDENTIFIER LPAREN functionArguments? RPAREN SEMICOLON;
+
+functionArguments:
+    functionArgument (COMMA functionArgument)*;
+
+functionArgument:
+    STRING_LITERAL | NUMBER | IDENTIFIER;