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 #6697, #6698, #6699, #6700 (quick gate green, 6003 passed each batch); 0 ejected. Fixed develop red (pre-merge-selection-selftest, stale oracle title from #6696) via #6700; develop tip 8b62e808 passes. Memory: none applied.