Merge lane base check: develop 60f0012f97b4

Merge lane base check: run the full gate on `develop` at `60f0012f97b46547aeb2cf3adb2bf210a0a78aa9` 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.

Certified develop 60f0012f97b4: full gate green (59934 tests, tree 2ac62a6b1a). Queue empty; #7171 merged. Nothing ejected. Memory: used mem-27640; proposed none.