Merge lane base check: develop c9cdf2a68ae9

Merge lane base check: run the full gate on `develop` at `c9cdf2a68ae9eaa80344e62fa3b1aac85308e2d3` 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).

develop c9cdf2a68 RED (reported develop_red): 54611 passed, 1 deterministic fail — test_cron_activity_runner [draft-True] still expects drafts to block after 27e0cf0a6 (Task 8283) made them non-blocking. Fix task #8347 already active. Nothing merged/ejected. Memory: none applied.