Turn a blog post, article, notes, or any source material into a set of vertical poster images — one cover plus several coherent content slides that explain the core points. Renders HTML/CSS to exact-size PNGs via headless Chrome. Use whenever the user wants cover art, 讲解图/配图, carousel slides, 封面图, poster series, or "content images" from an article/文章/素材/文件, especially for blog, 公众号, 小红书, or social posts. Default output is 1080×1920 PNG named 1.png (cover), 2.png, 3.png … written to the current working directory (the project the user is in) — never the source file's directory.