Merge lane base check: develop d79a6f56b945

Merge lane base check: run the full gate on `develop` at `d79a6f56b94539cd5434b41f257984669c92cfba` 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 d79a6f56b945: RED (full gate, 54740 passed, 3 failed). Failures: vitest WelcomePage git_connect=connected, and test_signup_schema email_signups columns, likely from PR #6461. develop_red reported, fix task left to the CP, lane not held. Memory: none applied.