Normalize + validate a phone number for requestPairingCode(): returns the
clean digits-only E.164 number, strips a leading "00" international call
prefix, and throws a descriptive TypeError for junk input, local-format
numbers (leading 0) and numbers over the 15-digit E.164 maximum.
Normalize + validate a phone number for requestPairingCode(): returns the clean digits-only E.164 number, strips a leading "00" international call prefix, and throws a descriptive TypeError for junk input, local-format numbers (leading 0) and numbers over the 15-digit E.164 maximum.