Merge lane base check: develop 882ccba94a77

Merge lane base check: run the full gate on `develop` at `882ccba94a77d32a68946f7d15382150a6d6125b` 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 882ccba94a77 certified: full gate green (65,016 passed) after one API-unit flake that passed its focused rerun; nothing ejected, develop green.