Merge lane base check: develop 5927384ee4df

Merge lane base check: run the full gate on `develop` at `5927384ee4dfd7dd713b895620b2bb3a54423dfd` 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 5927384ee4df certified: full gate green via merge_lane.py run (54675 passed, 0 failed, 735s). Nothing merged/ejected; integration branch green. Memory: none applied.