discussion: add devbox.json for pinning the nodejs version for consistent nodejs environment

hi, following up on the reproducible builds pull request #151 , i would like to propose two additional changes in a separate pr.

first, adding a devbox.json file to pin the node.js version so all developers use the same environment, since different node.js versions can sometimes produce slightly different build outputs.

second, adding a small section to the readme that documents how to verify reproducible builds by running npm ci, building twice, and comparing file hashes.

please let me know if these additions would be welcome and i can submit them as a separate pull request to keep changes focused.

Read the reproducible-builds pull request #151 and inspect the current build instructions. Add the proposed devbox.json pin and a README section covering npm ci, two builds, and file-hash comparison; done means both additions are present and the verification steps are documented.

Written by the indexing model from the issue text.