Merge lane base check: develop 621a776a10c3

Merge lane base check: run the full gate on `develop` at `621a776a10c3594c302ac770d732c98907d09a40` 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 621a776a10c3 reported develop_red: test_org_transfer_node.py:713 test_a_refused_move_writes_one_refused_row_and_moves_nothing fails on all 3 gate runs (no org_transfer_refused audit row on a stale-plan 409). Memory: none applied.