Merge lane base check: develop bd642215dd7a

Merge lane base check: run the full gate on `develop` at `bd642215dd7a38d730c832c0ba26da5c45440d94` 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 bd642215dd7a RED (lane reported develop_red): 3 API unit failures — durable enqueue seam, tenant_gmail activity-log key, token_billing outbox DBOS retry. Fix task to follow per contract; lane not held.