Single-file migration from a precise spec

Write a precise spec for migrating one low-risk file - exact target syntax, what not to change, expected test outcome - hand it to the agent, and complete the migration. Record every intervention you made and why in logs/interventions/t3-p1-02.json.

Starting with a low-risk file and a tight spec establishes your control condition. You cannot tell whether a looser spec costs you anything without this measurement first.