Merge lane base check: develop 98b0031c3073

Merge lane base check: run the full gate on `develop` at `98b0031c3073e4cdfca58505f425227a733eb8b5` 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 98b0031c3073 red (develop_red reported by merge_lane.py run): flaky — run 1 failed test_activity_capture_write::test_a_refused_mutation_is_recorded_with_its_status (passes alone); run 3 xdist worker crash in token_billing/test_outbox. Memory: none applied.