This skill should be used when the user says "plan infra change", "arn-infra-change-plan", "infra change plan", "plan this infrastructure change", "create infra plan", "arn infra plan", "plan the infra spec", "infrastructure implementation plan", "infra plan from spec", "generate infra plan", "plan infrastructure", or wants to generate a phased implementation plan from an infrastructure change specification, structured by provisioning order, blast radius, rollback checkpoints, and environment promotion gates.