描述
Manage the lifecycle of ExecPlans — self-contained, living specifications for multi-step work. Creates plans in the correct format, enforces living section updates, and handles the active → completed transition. Use for any work expected to take more than one session or touching more than 3 files. Triggers: "create a plan", "write a plan", "start plan", "continue plan", "resume plan", "finish plan", "complete plan", multi-step features, refactors, or tasks spanning sessions.