* refactor: rename @open-pencil/codegen to @open-pencil/emit
In design tools codegen means design-to-code, which is dom-css's job and
Core's codegen tools'. The package builds and prints the syntax trees
exporters emit, so name it for that. It has not been released yet.
* fix: alias @open-pencil/emit to its source in Vite
The rename missed the escaped regex, so Vite resolved the package through
its built dist output.
