refactor(compiler): 修改词法错误信息为中文

- 将 LexicalException 类中的英文错误信息改为中文
- 例：将 "Lexical error: Illegal character sequence '@' at 2:19" 改为 "词法错误：非法字符序列 '@' at2:19"

src/main/java/org/jcnc/snow/compiler/lexer/core/LexicalException.java

@@ -11,7 +11,7 @@ package org.jcnc.snow.compiler.lexer.core;
  * </ul>
  * <pre>
  * 例：
- *     main.s:2:19: Lexical error: Illegal character sequence '@' at 2:19
+ *     main.s:2:19: 词法错误：非法字符序列 '@' at 2:19
  * </pre>
  */
 public class LexicalException extends RuntimeException {