Merge lane base check: develop e9e72147b217

Merge lane base check: run the full gate on `develop` at `e9e72147b217498e85cb964fe6cfa45d6ccaafb2` 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 e9e72147b217 certified — full gate green (56078 passed, 0 failed, 662s), certified event recorded (tree 1a7617f). Nothing merged or ejected; develop is green. Memory: none applied.