Copies the package template to ~/.codeagent/settings.json (user scope)
or .codeagent/settings.json (project scope). The template uses placeholder
values – edit it to add real endpoint names and tier mappings. Store your
API key in .Renviron as CODEAGENT_API_KEY, never in settings.json.
Usage
use_codeagent_settings(scope = c("user", "project"), open = interactive())