实验：正则表达式转 NFA (Thompson 算法)
输入正则表达式（支持 |, *, ())，自动生成对应的非确定有限自动机 (NFA)。
Supports:
Simplified Mode: Reduces ε-transitions by merging states where possible (e.g. 1--a-->2 instead of 1--ε-->1'--a-->2'--ε-->2).
( ), | (union), * (closure), concatenation (implicit). Simplified Mode: Reduces ε-transitions by merging states where possible (e.g. 1--a-->2 instead of 1--ε-->1'--a-->2'--ε-->2).