unit-layer mutation sweep

open   by a73x

Labels: backlog, test

Banked since M11, evidence accumulating. M11: two findings were resolved by unit-layer pins discovered by accident while aiming an e2e campaign. M13: the stop_req resurrection was killed at unit AND e2e, unit failed first and cheapest. M15: all three regrade mutants were caught at the unit layer alone, none needed e2e — a third argument, not payment (three aimed mutants are not a sweep). A sweep aimed at the unit layer would not need the accident. See decisions.md M11/M15.