RCAL-927: Add ref_file entry for reference pixel subtraction reference file

[PaulHuwe]

Resolves RCAL-927

Closes #

This PR adds ref_file entry for reference pixel subtraction reference file.

Tasks

• update or add relevant tests
• update relevant docstrings and / or docs/ page
• Does this PR change any API used downstream? (if not, label with no-changelog-entry-needed)
  • write news fragment(s) in changes/: echo "changed something" > changes/<PR#>.<changetype>.rst (see below for change types)
  • start a romancal regression test with this branch installed ("git+https://github.com/<fork>/roman_datamodels@<branch>")

news fragment change types...

• changes/<PR#>.feature.rst: new feature
• changes/<PR#>.bugfix.rst: fixes an issue
• changes/<PR#>.doc.rst: documentation change
• changes/<PR#>.removal.rst: deprecation or removal of public API
• changes/<PR#>.misc.rst: infrastructure or miscellaneous change

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.77%. Comparing base (087a60d) to head (0a679d9).
Report is 55 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #397      +/-   ##
==========================================
+ Coverage   97.56%   97.77%   +0.21%     
==========================================
  Files          30       36       +6     
  Lines        2788     3461     +673     
==========================================
+ Hits         2720     3384     +664     
- Misses         68       77       +9     

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[PaulHuwe]

Regression Tests:
https://github.com/spacetelescope/RegressionTests/actions/runs/11208792665

[braingram]

Changes look good to me.

Regression tests show only the expected failures from the new refpix:

   {'dictionary_item_added': ["root['roman']['meta']['ref_file']['refpix']"]}

Waiting to approve until spacetelescope/rad#458 is merged and the rad requirement updated to main.

[braingram]

Thanks for updating the RAD pin.