Render Regulex-style railroad diagrams for a JavaScript regular expression and export the exact same SVG/PNG as the Regulex-Plus web UI (docs/index.html) "Export Image" feature. Use when the user provides a regex and wants an image for documentation, sharing, debugging, or embedding; output should match the web UI rendering rather than a re-implemented diagram. Supports flags i/m/g.

为 JavaScript 正则表达式生成类似 Regulex 的铁路图，并导出与 Regulex-Plus 网页界面（docs/index.html）“导出图像”功能完全一致的 SVG/PNG 图像。当用户提供正则表达式并需要用于文档、分享、调试或嵌入的图像时使用，输出应与网页界面渲染效果一致，而非重新实现的图表。支持 i/m/g 标志。