extractPositionals array invariant

extractPositionals() must always classify positional arrays as required and variadic. Trap: deriving optionality from Stricli’s minimum looks correct because minimum controls parser cardinality, but extraction represents the project’s fixed public positional contract, not raw parser permissiveness. Fix: preserve required: true and variadic: true for every extracted positional array and enforce this with property and unit regressions; flags retain separate requiredness rules.