Merge lane base check: develop cce1b2c44218

Merge lane base check: run the full gate on `develop` at `cce1b2c4421835cd219c1d507f1506e7dbeb8293` 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 cce1b2c44218 CERTIFIED via merge_lane.py run — full gate green in 682s (58,029 passed, 0 failed); prior plan-providers e2e red fixed by #6893. Nothing merged/ejected; develop green. Memory: none applied.