Merge lane base check: develop de88ae9c68b0

Merge lane base check: run the full gate on `develop` at `de88ae9c68b051c11cfcad0ec6cde1b10fdd34f3` 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 de88ae9c68b0 red (reported develop_red): 4 migration tests fail on missing FK fk_gha_runner_pools_credential_id_org (likely #7506); test_replay_codex usage_limit assertion fails; both fail again when rerun alone. Memory: none applied.