Add tf shape enum

[chris-ashe]

Description

Checklist

I confirm that I have completed the following checks:

• My changes follow the PROCESS style guide
• I have justified any large differences in the regression tests caused by this pull request in the comments.
• I have added new tests where appropriate for the changes I have made.
• If I have had to change any existing unit or integration tests, I have justified this change in the pull request comments.
• If I have made documentation changes, I have checked they render correctly.
• I have added documentation for my change, if appropriate.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 61.53846% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 47.52%. Comparing base (be8b546) to head (fb22fc3).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
process/models/tfcoil/base.py	62.50%	3 Missing ⚠️
process/core/init.py	60.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4130      +/-   ##
==========================================
+ Coverage   47.51%   47.52%   +0.01%     
==========================================
  Files         141      141              
  Lines       29537    29543       +6     
==========================================
+ Hits        14035    14041       +6     
  Misses      15502    15502              

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