nature-figure-prompt-only 是做什么的？
Generates image prompts for paper framework diagrams, flowcharts, and mechanism schematics using scientific expression and visual planning methods of Nature-style figures, but does not render images. When no image is provided, it reads the manuscript and generates prompts for new diagrams; when an image is provided, it generates visual improvement prompts while preserving the content. After outputting the prompt, it must stop and wait for confirmation—it does not call Imagegen or OpenRouter, generate Python/R/SVG code, or modify the research methodology. Suitable for back-end comparisons with other prompt skills.