Optionality via variants

ral has no Option type and no null. Optionality — a value that may be present or absent — is expressed as an open variant, idiomatically `some v and `none, passed as an ordinary value and discriminated by case.

This follows from two other commitments:

• Arguments are not where optionality lives, because every invocable has fixed arity: the caller always supplies every argument, and the value it supplies carries the presence or absence.
• Absence is data, not a sentinel: a null that inhabits every type reintroduces exactly the silent collapse the value/command separation removes.

A variant makes the two cases distinct in the type and forces the consumer to handle both.

Record fields give a second, structural route to the same end — scoped labels and spread shadowing express defaults and optional fields at the level of data.

This is a hard rule: do not add an Option/Maybe builtin or a null literal; reach for an open variant.