[mikekryjak]

Add PR template like in Hermes-3:

### Purpose
<!-- What problem does this PR solve, or what capability does it add? Provide a link to any relevant issues or pull requests. -->

### Breaking changes and changes to results
<!-- Does this PR require changes to existing input files, scripts, or workflows?
     Does it change physics results for existing inputs?
     Describe the changes, their rationale and any migration steps needed. -->

### Change Summary
<!-- Briefly describe what was changed. -->

### Validation
<!-- How did you verify this works? Include relevant tests, manual checks, or analysis. If not tested, say why. -->

### AI Assistance
<!-- Were AI tools used during development? If yes, briefly describe how, and how you verified their output. Remove this section if your PR does not contain AI-generated content. -->

### Documentation
<!-- What documentation was updated? If none, explain why no documentation changes were needed. -->

### Review Notes
<!-- Anything reviewers should pay particular attention to? For example: risks, limitations, things you're not sure about. -->