libnpmpack Programmatic Packing API

libnpmpack provides the programmatic interface for creating tarballs of npm packages, mirroring the functionality of the `npm pack` command-line tool. As an internal library of the npm CLI, it offers a robust and consistent way to prepare packages for distribution, including handling `.npmignore`, `.gitignore`, and package lifecycle scripts during the packing process. The current stable version of the `libnpmpack` package itself is 9.1.5, though it is often consumed as part of the broader npm CLI, which follows its own release schedule (e.g., v10.x and v11.x branches) and sees frequent updates. Its release cadence is tightly coupled with the npm CLI's monorepo development. A key differentiator is that it's the authoritative, low-level implementation for `npm pack`, ensuring compatibility with npm's official packing logic, unlike third-party alternatives which might deviate in edge cases. It focuses on encapsulating the complex logic of package bundling and file inclusion rules.