Optional addons on top of Nu core. Each domain is a self-contained package: a DSL for a category of problem, plus the Ref blueprints, queries, and commands it ships with. Nu core doesn't depend on any of them; they sit on top.
Today there is one domain:
- 00-shapes.md - the document-model domain. DSL for declaring structured data; ships the structured-Ref family for typed path navigation.