Merge lane base check: develop b8f6e6032071

Merge lane base check: run the full gate on `develop` at `b8f6e6032071cf032aa83689e4377f5f5c2d652c` 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 b8f6e60 certified: full gate green (62016 passed, 0 failed); nothing ejected, queue empty. Memory: none applied.