Compare Protocols Endpoint

Compare two UCPs and report the differences that change what a cycler does.

Cosmetic respellings are not differences: regenerated names, number formatting, redundant nesting, an explicit goto where fall-through was implicit, and a dropped trailing End all leave behaviour unchanged. What is reported is what reaches the cell -- loop counts, setpoints, terminations, gotos, safety bounds, and block-cumulative durations.

Pair it with /protocols/convert to check a round trip: convert a UCP to a vendor format, parse the result back with /protocols/parse, and compare the two UCPs. A difference there is a conversion that lost something.