Merge lane base check: develop 9d81b5dcb44a

Merge lane base check: run the full gate on `develop` at `9d81b5dcb44a1f212edea7171feb08d97b938a0c` 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 9d81b5dcb44a red (develop_red reported): test_tasks_routes_listing.py:261 renumbers a task to named*10+1, overflowing int4 tasks.id once the test sequence is high. Test bug, not product; lane files the fix task. Memory: none applied