Merge lane base check: develop 93b0d4a5c444

Merge lane base check: run the full gate on `develop` at `93b0d4a5c4442ae1a8b628fb593af53dc587091d` alone and report it certified or red: nothing had certified it since the last attempt. A red verdict files a fix task; it never holds the lane. Filed by the control plane (`app/merge_lane.py::_certify_idle`). How: run `python3 tools/merge_lane.py run` once. It takes this check's batch, gates that commit with the full gate in its sandbox and reports `certified` or `develop_red` itself. Never run the gate by hand: a hand-run green reports nothing, so no certificate is recorded.

develop 93b0d4a5c444 certified green (full gate, 59879 passed). First attempt red on flaky jaahd test test_replay_pi.py::test_closes_no_spend_reading; green on rerun of identical tree. Memory: none applied.