Merge lane base check: develop 9f142590aa87

Merge lane base check: run the full gate on `develop` at `9f142590aa871d23d4da1aa4278212095e5f5062` alone and report it certified or red, beside lane run 10465. Filed by the control plane (`app/merge_lane.py::request_base_check`). 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 (Task 6722).