Add comprehensive Chinese documentation to Tokenizer and CSTBuilder

[Copilot]

Added detailed Chinese comments to Tokenizer.js and CSTBuilder.js to make the lexical analysis and CST construction logic accessible to developers unfamiliar with AST/CST concepts.

Changes

Tokenizer.js

• Class-level documentation explaining tokenization and the Token concept with concrete examples
• Method documentation for all parsing logic (strings, numbers, keywords, comments, punctuation)
• Inline comments describing character-by-character parsing decisions

CSTBuilder.js

• Class-level documentation clarifying CST vs AST differences and why CST preserves formatting
• Method documentation explaining the recursive descent parsing strategy
• Step-by-step inline comments for object and array parsing, including trivia handling

Documentation approach

Comments explain:

• What each component does and why it exists
• Key concepts (tokens, CST, trivia) with plain language definitions
• Concrete examples of input/output transformations
• Step-by-step breakdown of complex parsing logic

Example from Tokenizer:

/**
 * 读取数字
 * 
 * JSON 数字格式支持：
 * 1. 整数：123
 * 2. 负数：-123
 * 3. 小数：123.456
 * 4. 科学计数法：1.23e10 或 1.23E-5
 */
readNumber() {
  const start = this.pos;
  // 1. 处理可选的负号
  if (this.text[this.pos] === "-") this.pos++;
  // ...
}

Original prompt

请用中文注释，标注清楚 Tokenizer 和 CSTBuilder 的代码实现细节，让不了解 AST/CST 的开发者能够通熟易懂的阅读

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