Use this skill whenever the user wants to analyze a codebase and generate a detailed product spec document. Triggers for: "analyze this codebase", "generate a spec", "document this project", "reverse engineer this app", "what does this system do", "create product documentation", "map out the features", "extract product rules from code", "what does this codebase do", "generate product spec from code", "document this app", "spec out this repo", "read this code and tell me what it does", "create a product spec", "reverse engineer the product", "what features does this app have", "document the flows", "extract the prompts from this code", or any request to extract product knowledge from source code. Supports any input method: file uploads, pasted code, filesystem paths, or zip archives. Always use this skill when the user shares code AND wants to understand what the product does — even if they don't explicitly say "spec" or "documentation".