Merge lane base check: develop 60c9effafd8a

Merge lane base check: run the full gate on `develop` at `60c9effafd8a6101064458d873ebd4fcc4a73d05` 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 (Task 6722).

Base check certified: develop 60c9effafd8a green on full gate via merge_lane.py run (654s, 56648 passed, 0 failed, tree 27f7f1b7). Nothing merged or ejected; develop green. Memory: none applied.