Agent Skills: plan

Research-and-plan mode for substantive tasks before implementation. Use when the user asks to plan, design, investigate, figure out, or explore how to make a non-trivial code change. Restricts the agent to read-only operations until the user explicitly authorizes implementation. Grounds every claim in the codebase and current docs instead of memory, keeps a full rewrite and rejecting the task itself on the table, and opens with the before and after that the project's users will feel.