Create a fresh starter site in dir: a .docuriser-site config seeded with title, a default home.sections layout (description → projects → socials, plan 03), and an empty content-fragments/ dir for future custom sections. Shared by the CLI (docuriser site init) and the GUI's New Website dialog so the two never drift on what a brand-new site looks like.

Creates dir (and parents) if missing. Returns false — and sets *error when given — if dir can't be created or already contains a .docuriser-site (existing sites are never overwritten). On success the site is ready to open or build.