Merge lane base check: develop a43a53803dd4

Merge lane base check: run the full gate on `develop` at `a43a53803dd41f623fd7e53e1ed7210eac191247` 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 develop a43a53803dd4: RED (merge_lane.py run, full gate 2×). 56942 passed, 4 failed — frontend-unit-vitest: is_superadmin census tests (allowlisted operator-only gate / pinned subject read). develop_red reported; queue empty. Memory: none applied.