Merge lane base check: develop 902bbda740a6

Merge lane base check: run the full gate on `develop` at `902bbda740a66c7c4f18f5621a7a8d9740897796` 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 902bbda740 is red: merge_lane.py reported develop_red. 12 apps/api tests fail on their own every time (mostly test_routers_cloud cloud-only /api/outcomes* and agent-index routes, plus activity_kinds, cross_org_isolation, plan_engine, blind_checkout). Memory: none applied