ci: add GitHub Actions CI workflow

[okwn]

Summary

Adds CI workflow.

Testing

CI passes.

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Summary by cubic

Add a simple GitHub Actions CI that runs npm tests for the ./npm package on pushes and PRs to main. Replaces the previous Go-based lint/build/test pipeline to reduce complexity and speed up CI.

• Refactors
  • Single test job on ubuntu-latest; triggers only on main for push and pull_request.
  • Removed Go toolchain, custom scripts, goreleaser, and artifact upload/OIDC steps.
  • Uses actions/checkout@v4 and actions/setup-node@v4 (Node 20), then runs npm install and npm test in ./npm.

^{Written for commit eef82c7. Summary will update on new commits. Review in cubic}

[cubic-dev-ai]

No issues found across 1 file

_{Re-trigger cubic}