Set up CI/CD with GitHub Actions

[engichang1467]

Create CI Workflow to Run Smoke Tests

We need to automate our testing to ensure pull requests do not break existing functionality.

Tasks:

• Create a workflow file at .github/workflows/test.yml.
• Configure the workflow to:
  • Trigger on push and pull_request.
  • Set up Python 3.11.
  • Install dependencies using uv (refer to ops/set_up_env.sh logic).
  • Run the following smoke tests:
    • tests/test_encoder.py
    • tests/test_decoder.py
    • tests/test_loss.py
    • tests/test_rig3r_forward.py