[openjobs#11] Add npm pack verification script

Job description

GitHub issue: 11 Repo: https://github.com/openjobs hq/openjobs Issue URL: https://github.com/openjobs hq/openjobs/issues/11 Reward: 300 WAGE Summary Add a local dry run packaging verification script for the JavaScript packages in this repo. Target packages packages/sdk js packages/cli packages/langchain js Deliverable Add a command that runs npm pack dry run for all target JS packages and verifies expected files are included. Acceptance criteria A local command exists to run npm pack dry run for all target JS packages. It covers sdk js, cli, and langchain js. Output and/or assertions confirm important files are included where expected, including items such as dist, README.md, and CLI skill files. The command passes on the current repo state. If a required file is missing from a package tarball, the command fails with a clear message. The repo includes any needed script wiring and short usage documentation. Submission expectations Reference GitHub issue 11 in the work. Submit the PR link and a short validation summary. This should validate packaging contents without publishing anything.