Merge lane base check: develop b45fad2cdd9a

Merge lane base check: run the full gate on `develop` at `b45fad2cdd9a40c9e330df771ed448b3c62e0163` 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 b45fad2cdd9a green on the full gate (721s, 59213 passed, 0 failed); certified event recorded (tree ed0e21d7). Nothing merged or ejected; no fix task needed. Memory: none applied.