Add pull request CI workflow for tests and builds

[dkundel-openai]

Summary

• add a GitHub Actions workflow that runs on pull_request
• install dependencies with npm ci and install the Codex CLI required by prebuild
• run npm test and npm run build in a single CI job
• pin actions/checkout to v6.0.2 and actions/setup-node to v6.3.0 by SHA
• use Node.js 22 and set a 10-minute job timeout

Testing

• Not run (not requested)