Merge lane: jaah

Merge lane run: batch the queued PRs, run the full gate (if any) once on their merged tree, and merge the batch when it is green. Filed by the control plane (`app/merge_lane.py::ensure_lane`).

Merged 5 PRs in 4 quick-gated batches: #6234, #6235, #6236, #6237, #6238. None ejected, queue empty. develop is green at dc7e0d1. The queue's develop_red flag (Vale, 686a2b3) is out of date: Vale passes on current develop.