Properly interpolate starfield models and use correct time windows

[lowderchris]

Updates to starfield subtraction

[codecov]

Codecov Report

❌ Patch coverage is 12.76596% with 41 lines in your changes missing coverage. Please review.
✅ Project coverage is 57.28%. Comparing base (e4af56b) to head (22279ca).
⚠️ Report is 14 commits behind head on main.

Files with missing lines	Patch %	Lines
punchbowl/level3/stellar.py	17.39%	19 Missing ⚠️
punchbowl/auto/flows/level3.py	0.00%	16 Missing ⚠️
punchbowl/util.py	25.00%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #932      +/-   ##
==========================================
- Coverage   57.39%   57.28%   -0.11%     
==========================================
  Files         125      125              
  Lines       13887    13921      +34     
==========================================
+ Hits         7970     7975       +5     
- Misses       5917     5946      +29     

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[jmbhughes]

I think this is good, but I'm tired and might wait to merge until morning so I can see it with fresh eyes.