Internal npm registry (anpm) only allows specific scopes like @ali,
not @alibaba-group. Derive scope from OCR_PKG_NAME and apply it to
platform subpackage names during publish. Also make platform.js read
package names from optionalDependencies dynamically instead of relying
solely on the hardcoded scope.
Ship Go binaries inside per-platform npm packages (@alibaba-group/ocr-{os}-{arch})
so npm install resolves the correct binary via optionalDependencies + os/cpu fields.
This removes the need for a postinstall download from GitHub Releases, which is
extremely slow for users behind restricted networks (e.g. China mainland).
The postinstall download is retained as a fallback for --no-optional installs.