Merge lane base check: develop 833e0cfdc939

Merge lane base check: run the full gate on `develop` at `833e0cfdc939e2f11bda73ff63a36e9effaf6907` 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 833e0cfdc939 red (develop_red reported): test_git_access::test_no_cookie_authenticated_get_mutates_state — GET /api/tasks/{id}/page writes via _isolation (likely PR #7505, Task 11882). Memory: none applied