IV.5 Data and schemas

• Do not change a field's type — add a new field and mark the old one @removed.
• oxl.schema.lock goes into git, changes in it go through review.
• Money is Money/Decimal, not f64. Identifiers are distinct types (UserId), not bare u64.
• Input data — with refined types (Email, Port), so that validation happens during decoding.

Source: docs/spec/oxl-standard.en.md