Generate 4-6 complete candidate design systems for a web project, let the user pick one visually in the browser, and freeze the winner into a Google-spec design.md at the project root. Use ONLY when the user explicitly invokes /design-md or explicitly asks to run the design-system picker. If a conversation merely suggests it would help, suggest it — never start it unasked (it launches a server, opens a browser, and writes many files).