Merge lane base check: develop e5f0eecd5a59

Merge lane base check: run the full gate on `develop` at `e5f0eecd5a59c057fb1f55f3367371739bcc07b5` 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).

develop e5f0eecd5a59 certified green by merge_lane.py run (full gate: 58096 passed). One flake (e2e/add-node-dialog.spec.ts:355) failed once, passed on focused rerun + full rerun. Nothing merged/ejected; queue empty. Memory: used mem-25266; none proposed.