Merge lane base check: develop ab51b9a7fbe2

Merge lane base check: run the full gate on `develop` at `ab51b9a7fbe24c353235ef2a0e308eef1e87e905` 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.

Base check develop ab51b9a7: RED, reported develop_red. 64764 passed, 2 failed in Frontend unit (vitest): apps/web/src/mutedText.test.ts (palette path computed into Typography/Link color). Fix task filed by CP; nothing ejected. Memory: none applied