Merge lane base check: develop a66ee1af7538

Merge lane base check: run the full gate on `develop` at `a66ee1af7538bd05c998ffd9a075106448c9f9e5` 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 a66ee1af7538: certified green (full gate 874s, 59,489 passed, 0 failed; one flake retried green). No PR needed. Queued PRs left to the main merge lane. Memory: none applied.