JP-3307: Add metadata keywords to schema for ta_center step

[emolter]

Part of JP-3307

Is blocked by spacetelescope/jwst#10035

This PR adds the cal_step status for the new targ_centroid step, adds source_xpos and source_ypos header keywords to store the results of that step, and adds ta_xpos, ta_ypos keywords to store the "true" position of the source in the TA verification image (prior to applying filteroffset)

See spacetelescope/jwst#10011

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)
  • run jwst regression tests with this branch installed ("git+https://github.com/<fork>/stdatamodels@<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 90.33%. Comparing base (dcea963) to head (1818c4c).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #620      +/-   ##
==========================================
+ Coverage   90.32%   90.33%   +0.01%     
==========================================
  Files          99       99              
  Lines        4674     4679       +5     
==========================================
+ Hits         4222     4227       +5     
  Misses        452      452              

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[emolter]

regtests with jwst main: https://github.com/spacetelescope/RegressionTests/actions/runs/19579002977

regtests with jwst PR branch: https://github.com/spacetelescope/RegressionTests/actions/runs/19578975714

[emolter]

regtest rerun against main: https://github.com/spacetelescope/RegressionTests/actions/runs/19689393898

Differences are expected: they add SRCXPOS and SRCYPOS keywords to MIRI LRS slit and slitless data only

[emolter]

New regtest runs, which don't add metadata to the ImageModel and CubeModel because we're going to use SlitModel for MIRI LRS now, show no differences:
https://github.com/spacetelescope/RegressionTests/actions/runs/19689393898

[emolter]

@melanieclarke all three comments should be addressed by d4027da

[melanieclarke]

This all looks good now, thanks! I'm reviewing the jwst PR now, though, so let's leave this one open for a bit in case there are further changes needed.