Merge lane base check: develop bbedc19f38ff

Merge lane base check: run the full gate on `develop` at `bbedc19f38ff75f6515197c926c4f78bb231427f` 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 bbedc19f38ff: RED (develop_red reported). Full gate 54,973 pass / 1 fail: e2e/task-detail-fit.spec.ts:646 (448x900 wrapped-trail ›), fails again alone. Nothing merged/ejected by this run; #6423 merged, queue empty. Memory: none applied.