Merge lane base check: develop fdf7f681522c

Merge lane base check: run the full gate on `develop` at `fdf7f681522ca9fd6f3083c5df5e41839242ea4d` 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`). How: run `python3 tools/merge_lane.py run` once. It takes this check's batch, gates that commit with the full gate in its sandbox and reports `certified` or `develop_red` itself. Never run the gate by hand: a hand-run green reports nothing, so no certificate is recorded (Task 6722).

Base check develop fdf7f681522c: RED (lane reported develop_red). 1 failure, reproduced alone: jaahd test_git_worktree_add_has_exactly_one_home_in_production_code flags gitops.py:53 `git(worktree,"add","-A")` from PR #7088 (Task 10482), a regex false positive. Nothing merged. Memory: none applied.