Agent Skills: create-team

Creates and manages an agent team (planner + implementer teammates) for the current worktree session. Use when user says "create team", "팀 생성", "팀 만들어줘", "agent team", or wants a planner+implementer spec-driven workflow in a worktree session. Also covers team operations — cleanup ("팀 정리", end teammates) and expand ("팀원 추가", add a role) — folded from the former agent-team commands.