Execute an implementation plan with rigorous checklist-driven verification. Every task is pre-flighted, worked, validated with proof, and checked off. Every phase is validated as a whole. If proof is missing, the agent goes back. Honesty is non-negotiable — broken trust means the plan is not done. Triggers: 'implement this plan', 'execute the plan', 'start working on the plan', 'do the plan', 'carry out the phases', 'run the plan', 'work through the plan', 'carry out this plan', 'begin implementation'. Do NOT use for plans that have not been reviewed — use plan-review first.