The suite's tests came from #98780 written against an invented holder shape (handles/node); the engine resolves through holder.book/holder.url after an elements inventory. Address elements the way the agent does (firstRef), stub document.execCommand (undefined in jsdom), and add the execCommand-fails fallback case. Co-authored-by: salch-cred <salch-cred@users.noreply.github.com>