addPhone

Adds a typed vcard:hasTelephone entry on a counter-labelled blank node (_:phone{n}). PhoneType.OTHER entries are written without a type triple, byte-compatible with legacy writers. Does nothing and returns false when number is blank or already present.

The stored value is a valid tel: IRI: RFC 3966 visual separators (spaces, parentheses, dots, hyphens, slashes) are stripped and any remaining IRI-illegal character is percent-encoded, so "+31 6 12 34 56 78" is stored as tel:+31612345678.