Merge lane base check: develop 54ade235ffdb

Merge lane base check: run the full gate on `develop` at `54ade235ffdbfde70afa3224483c2869390083d8` 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 54ade235 red: test_cross_org_isolation::test_every_path_parameter_is_swept_or_named — `legacy_id` still in _UNSEEDED_PARAMS after PR #7560 retired its route; confirmed on focused rerun. develop_red reported via merge_lane run.