.github/PULL_REQUEST_TEMPLATE.md

## Summary

Describe the change and why it is useful.

## Validation

- [ ] Tests added or updated
- [ ] `python -m pytest` passes
- [ ] Relevant CLI commands were smoke-tested
- [ ] Documentation and changelog were updated
- [ ] No secrets, private media, generated outputs, or unlicensed assets are included
- [ ] New third-party tools or models are credited with license notes

## Privacy and compatibility

Describe any changes to data handling, network behavior, supported platforms, or installation requirements.