### Added
- Support union types on parameters and class/trait properties: a `type | type | ...` prefix (builtin scalars, `null`/`false`, and `` casts) is emitted as an ordered `data-types` member list. Parameters additionally carry `data-type: "variable"`; the single-type and single-cast forms are unchanged. Mirrors the union return-type syntax already accepted after `->` ([zephir-lang/zephir#2613](https://github.com/zephir-lang/zephir/issues/2613)).