Merge lane base check: develop 4c0f7743871e

Merge lane base check: run the full gate on `develop` at `4c0f7743871e4c5624a356957dd4eb9a90b8ca90` 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 of develop 4c0f774: develop_red, reported by tools/merge_lane.py run. 3 Playwright tests fail on their own (company-setup-self-service:153, access-principal:178, org-upgrade:84). Likely cause: the plan-tab refactor in PR #6392. Nothing merged; queue empty. Memory: none applied.