Merge lane base check: develop f43dbb09f4b8

Merge lane base check: run the full gate on `develop` at `f43dbb09f4b8f595eaa9fd7c420f12ddc5a3c404` 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`).

RED: full gate on develop f43dbb09f failed python-types-mypy (202610201000_github_runners_cap.py:105 arg-type, :117 assignment; Task 8197) and docs-prose-lint-vale (subscription.md:84 'prefilled'; Task 8208). Same files on tip 0e7800cdb, still red. Nothing merged. Memory: none applied.