Agent Skills: review-diffs

Review git diffs with a manager-led workflow that preserves issue requirements. First derive a shared review contract from the user request and any linked issue or PR, then select review perspectives from a catalog (a mandatory floor plus diff-specific optional lenses, including a rendered UI/visual lens with web and Flutter-golden backends), run those perspectives as parallel tmux review agents, and finally perform a manager pass that checks total requirement coverage before summarizing.