Merge lane base check: develop e806b4044f94

Merge lane base check: run the full gate on `develop` at `e806b4044f941d35aa3efeb122b4750669e07834` 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 e806b4044f94 certified — full gate green via merge_lane.py run (678s, 57787 passed, 0 failed; tree 7a0ead54). Nothing merged or ejected; integration branch green. Memory: used mem-25266; none proposed.