Merge lane base check: develop 3bb104c61154

Merge lane base check: run the full gate on `develop` at `3bb104c611544fe645da76176ff68826986c6a1b` 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).

develop 3bb104c61154 certified green: merge_lane.py run full gate exit 0 in 733s, 58382 passed / 0 failed; event=certified. Queue empty, no breaches. Nothing merged or ejected. Memory: none applied.