Merge lane base check: develop 0970756859a6

Merge lane base check: run the full gate on `develop` at `0970756859a6c237c5a55bd6935afe9c236308a8` 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.

develop 0970756859a6 is red (reported develop_red). test_plan_routes.py::test_no_amount_but_the_price_mirror_can_feed_a_plan_response fails on its own: _snapshot now uses pick (0f053147b6, Task 11865), so the AST reader check no longer finds it. No rows ejected.