Merge lane base check: develop 98d9651d730d

Merge lane base check: run the full gate on `develop` at `98d9651d730de9ea4903cd40c9bd4e4ea381b298` 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 98d9651d730d RED (full gate 3×, develop_red reported): 3 tests/test_loop_debug.py tests fail under xdist (stray INFO record / duplicate handler), pass in isolation — from #7762 (Task 12733). Fix task filed by CP. Memory: none applied.