Merge lane base check: develop 5c71079ccc0c

Merge lane base check: run the full gate on `develop` at `5c71079ccc0c21c1af22fc90d7ff13c5317483e9` 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 (Task 6722).

develop 5c71079ccc0c RED (develop_red reported by merge_lane.py run): test_task_settle_folder.py::…[plan] fails twice (unpacks 1 terminal; plan now has coders+analysis since c2cede5c3, Task 10339). Fix: take PERSONA_TERMINALS[persona][0]. Memory: none applied.