Merge lane base check: develop 5299841ab283

Merge lane base check: run the full gate on `develop` at `5299841ab283a5f9ddf8a770a3a77beb84c0f5f5` 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 5299841ab283: RED, develop_red reported. 2 API tests fail on rerun alone (test_git_access no-cookie GET, test_workflow_registry catalogue). Fix task #8840 filed. Nothing merged. Memory: none applied.