ensuringArgumentIsFormatter
Reads the write_term/2,3 option list at index (via ensuringArgumentIsValidOptionList) and turns it into the TermFormatter it describes: quoted(true) selects QUOTED_IF_NECESSARY atom/functor quoting, ignore_ops(true) disables operator notation, and numbervars(true) renders '$VAR'(N) terms as letters. Options not present in the list default to false.