ci: build wheel only on origin, make sbom test more robust

[terriko]

• fixes ci: new "Build wheel (3.12)" job should not run on pull requests #4115

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.76%. Comparing base (d6cbe40) to head (1a9a8ee).
Report is 224 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4126      +/-   ##
==========================================
+ Coverage   75.41%   81.76%   +6.34%     
==========================================
  Files         808      820      +12     
  Lines       11983    12540     +557     
  Branches     1598     1943     +345     
==========================================
+ Hits         9037    10253    +1216     
+ Misses       2593     1872     -721     
- Partials      353      415      +62     

Flag	Coverage Δ
longtests	80.95% <100.00%> (+5.54%)	⬆️
win-longtests	79.76% <100.00%> (?)

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[terriko]

Well, that definitely didn't work.

[terriko]

K, working now and ready for review.