Merge lane base check: develop df0f952c32c0

Merge lane base check: run the full gate on `develop` at `df0f952c32c0519ad8c092bff0b51cf917d2780e` 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 df0f952c32 red (develop_red reported): test_exclude_done_keeps_the_task_the_term_names overflows int4 (renumbers to named*10+1 ≈ 4.2e9). Run 1's 5 failures passed on a focused re-run (flaky). No PR merged.