Merge lane base check: develop bce6624909ff

Merge lane base check: run the full gate on `develop` at `bce6624909ffc5c70a5f86e8714ce4036bb05003` 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 bce6624909ff red: full gate (2×) failed e2e/task-detail-fit.spec.ts:198 (1280x800 'names who settled each resolved round') in load-isolated Playwright smoke; merge_lane.py reported develop_red. Memory: none applied