move size check into arguments block

[ccreutzi]

Use mustBeValidSize in arguments block instead of validateSizeNVP later.

Closes #29.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 76.92308% with 3 lines in your changes missing coverage. Please review.

Project coverage is 60.98%. Comparing base (93a39af) to head (a6c86c8).

Files	Patch %	Lines
tests/topenAIImages.m	40.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #43      +/-   ##
==========================================
- Coverage   61.06%   60.98%   -0.08%     
==========================================
  Files          33       33              
  Lines        2052     2048       -4     
==========================================
- Hits         1253     1249       -4     
  Misses        799      799              

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

[adulai]

Adding comment to see if that will update my reviewer status.