Switch the npm package name from the unscoped `gitagent` (which the CI
NPM_TOKEN can't create) to the existing scoped `@open-gitagent/gitagent`,
which the token can publish. 1.5.0 > 0.2.0 so it becomes the new latest.
- package.json + package-lock.json: name -> @open-gitagent/gitagent
(bin stays `gitagent`, version stays 1.5.0)
- install.sh: scope npm ls/view/install + global-dir refs (the
`gitagent` command and display strings are unchanged)
- README + Documentation: install command -> npm install -g @open-gitagent/gitagent
npm ci + npm run build verified locally.