feat(nodejs): root entry, prebuilt, install script, package.json files for tarball

[vkozio]

Summary

• Root entry point and copy types for file: dependency.
• Prebuilt binary support and install script for GitHub installs.
• package.json "files": add prebuilt, src_js, install.js so install from GitHub tarball includes them and install.js runs (otherwise prebuilt/ and install fail).

Motivation

Enable install from monorepo path and from GitHub; optional prebuilt to avoid building from source. Fix tarball layout so pnpm/npm install from GitHub works.

Changes

• tools/nodejs_api: index.js, index.mjs, install.js, package.json (incl. "files"), package.js, docs.
• No CI in this PR; CI (including prebuilt push) can be proposed separately.

Testing

• make nodejs && cd tools/nodejs_api && npm test
• Install from GitHub (path:tools/nodejs_api or tarball): prebuilt/, src_js/, install.js present; install.js runs and populates build/