Merge lane base check: develop 2db102c46e02

Merge lane base check: run the full gate on `develop` at `2db102c46e02e83a79ba07bb348fad3ebc96355a` 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 certified: develop 2db102c46e02 passed the full gate (tree 6b08c5970b, 56,648 tests, 0 failed, 642s). Nothing merged or ejected; the queue is empty and develop is green. Memory: none applied.