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 #6703 (Task 9203) at 58b330707 after the quick gate passed on the merged tree (6014 tests). Nothing ejected. It fixes develop's red agent-sdk conformance stage, and packages/agent-sdk/check.sh now passes on develop. Queue is empty. Memory: none applied.