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 PR #6705 (Task 9208) as 6fd6578d; quick gate green on merged tree (6003 passed). 0 ejected, queue empty. develop_red record names superseded 58b33070 (fixed by #6704); base check 9209 on 63c148b0 running. Memory: none applied.