Agent Skills: spec-writing

This skill should be used when the user asks to "create a spec", "write a specification", "review a spec", "update a spec", "review spec organization", "split a spec", "add a page to spec", "remove a page from spec", "move requirements between pages", "add requirements", "review requirements", "update requirements", "delete requirements", "add tests", "add test cases", "review tests", "update tests", "delete tests", or needs guidance on spec structure, formatting, or spec writing best practices.