Generate a reusable design.md or DESIGN.md from a live website by deeply inspecting the site with `agent-browser` and `agent-browser eval`, then synthesizing its visual language, layout system, interaction patterns, and content style into a structured markdown design system. Use when given one or more website URLs and asked to analyze a site, reverse-engineer its design, extract its look and feel, write DESIGN.md, create a style guide, or capture a site's UI rules for later AI-assisted design or implementation. Prefer this skill when the goal is documentation rather than rebuilding the page in code. Always use `agent-browser` as the primary browser runtime; if it is missing, help the user install or expose it instead of switching platforms or browser stacks.