Test project

This project uses the delivery-probe library, which is not stored in this project. .cp-delivery-probe/library.md gives the library's location on this machine, and indexes its skills with their descriptions; cp-delivery-probe-init writes it. When asked to follow a delivery-probe instruction, or when a task matches a skill described there, find the file from there, read it, and follow it. If .cp-delivery-probe/library.md is missing, stop and tell the user to run cp-delivery-probe-init; do not look for the library anywhere else.