Merge lane base check: develop b022a8c4585b

Merge lane base check: run the full gate on `develop` at `b022a8c4585b74b8f1a0c623933bfa0943269976` 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 b022a8c4 red: test_cron_retention census matches the new headscale test name in tools/tests/test_jaah_deploy_steps.py:472 (afd4098aef, PR #7551) via the console/ mount — false positive, still red twice. Memory: none applied.