Merge lane base check: develop 642eaa0bb247

Merge lane base check: run the full gate on `develop` at `642eaa0bb247580072f789cdf5ba42cf264f0a07` 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 642eaa0bb247 red (2 failures): manifest.toml still lists apps/jaahd/rootlib/*.py under [check] carried, but shipped modules import it since 39931ad76d (Task 11727). Fix tracked in Task 11774. Memory: none applied.