feat: Add truth output

[HCookie]

Description

Add a truth output, which writes the truth from the input at the same time.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update

Code Compatibility

• I have performed a self-review of my code

Code Performance and Testing

• I have added tests that prove my fix is effective or that my feature works
• I ran the complete Pytest test suite locally, and they pass

Dependencies

• I have ensured that the code is still pip-installable after the changes and runs
• I have tested that new dependencies themselves are pip-installable.

Documentation

• My code follows the style guidelines of this project
• I have updated the documentation and docstrings to reflect the changes
• I have added comments to my code, particularly in hard-to-understand areas

Additional Notes

---

📚 Documentation preview 📚: https://anemoi-inference--144.org.readthedocs.build/en/144/

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.07%. Comparing base (90728d5) to head (8cbd11a).
Report is 56 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #144      +/-   ##
==========================================
- Coverage   98.03%   96.07%   -1.97%     
==========================================
  Files           3        3              
  Lines          51       51              
==========================================
- Hits           50       49       -1     
- Misses          1        2       +1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.