Merge lane base check: develop c8b7113e573f

Merge lane base check: run the full gate on `develop` at `c8b7113e573fe3aa284fdc8ce023ec9a31eecbf5` 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.

develop c8b7113e573f reported develop_red: 4 Playwright e2e fail deterministically (access-principal:165, access-tabs:140, nodes-roster-width:254/378 @448px); fix task filed by lane. Memory: none applied.