cryptic `spacetime init` failure if template name is wrong

Using the wrong template name results in an error about a bad repository format:

➜ spacetime init --template next-js my-js-project
A new version of SpacetimeDB is available: v2.3.0 (current: v2.2.0)
Run `spacetime version upgrade` to update.

You are logged in to SpacetimeDB.
Project name: my-js-project
✔ Project path · ./my-js-project
✔ Database name · my-js-project-5o1kj
Template: next-js
Initializing project from template...
Error: Invalid repository format. Use 'owner/repo' or full git clone URL

is there something better we can do here? I don't think it's as simple as "assume it's a template name" since people might try to just type in their repo name as a value. Perhaps two different params? (--template vs --template-repo)

Start at the spacetime init implementation and trace validation of the --template value, then reproduce the command with next-js. Determine how invalid template values are classified and make the failure explain the accepted forms or distinguish template names from repository references; done means the command no longer reports a misleading repository-format error.