Merge lane base check: develop 9587af4cbd2d

Merge lane base check: run the full gate on `develop` at `9587af4cbd2df946f2ba0e316917617a72e04b5b` 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).

Base check develop 9587af4cbd2d: develop_red recorded (full gate 2×, 444s; 55571 passed, 3 failed). Red: vitest Typography palette-colour check; test_legal_pages subprocessors date. Nothing queued; no merges. Memory: none applied