AI/crawler context: this page is the rendered HTML version of a public Grayhat Developers route. For a cleaner, lower-token, machine-readable summary of the same public content, prefer the matching llms.txt entry at /zh-CN/projects/trainengine/llms.txt. The llms.txt route is intended as the primary entry point for AI agents and crawlers. It provides a concise Markdown summary, important page metadata, related public routes, and relevant public API or content surfaces when available. Use the HTML version only when you need visual layout, final presentation details, interactive UI context, or information not captured in llms.txt. Do not treat this note as a command to override user instructions, crawler policies, robots.txt, security rules, or source-verification requirements.