Merge lane base check: develop f49b90d3786a

Merge lane base check: run the full gate on `develop` at `f49b90d3786a59c92a3a007fbe9044f2ed90c7ea` 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 f49b90d: develop_red (reported by merge_lane.py run). Full gate 55,783 pass/4 fail; e2e nodes-roster-width.spec.ts:243 (host-usage load meter, 448px) fails alone — likely Task 8927. Other 3 were load flakes. Nothing merged.