Merge lane base check: develop 1e87d0741613

Merge lane base check: run the full gate on `develop` at `1e87d074161302aa585135dca4a487839219c5da` 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.

develop 1e87d0741613 RED (reported develop_red): 10 TaskDetailPage vitest failures, stale after #7135's image thumbnails. Fix PR #7141 gated green but closed as superseded by #7139, already on develop (b9dc434). Nothing ejected.