Merge lane base check: develop 69c8b6fb0cff

Merge lane base check: run the full gate on `develop` at `69c8b6fb0cff6734fc38fed72c79d3f167e00d1e` 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 69c8b6fb0cff: RED. Full gate 59662 passed, 1 failed in Frontend smoke (playwright load-isolated); focused rerun red again (not a flake). merge_lane.py reported develop_red; nothing merged or ejected. Memory: none applied.