Internal helper returning the default project structure. Single source of
truth for init_project(), generate_project_config(), and
check_project().
Details
R/ holds the .R script derived from the project's .qmd source,
whether that derivation happens through qmd_to_r() or through the
post-render hook scaffolded by create_qmd(). scripts/ holds
hand-written, human-maintained scripts. The distinction matters because
downstream packages resolve the derived script by convention.
