Fix open boundaries with periodic boundary zone

[efaulhaber]

When simulating periodic boundaries top/bottom and open boundaries left/right, the boundary zones are periodic in tangential direction. This doesn't work on main, as fluid particles that passed through the periodic boundary (in the screenshot below particles from the bottom that appear at the top) don't get converted when entering the boundary zone.

Note the orphaned fluid particles at the top in this screenshot.

[efaulhaber]

Codex Review

The PR updates open-boundary particle classification and transfer to use periodic coordinates, with a regression test covering conversion near a periodic boundary. I did not identify correctness or regression issues in the changed production behavior.

This is an AI-generated code review. Please verify the findings and summary before acting on them.
_{Review generated by codex-pr-review}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.11%. Comparing base (5486242) to head (5d8caac).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1237   +/-   ##
=======================================
  Coverage   90.11%   90.11%           
=======================================
  Files         137      137           
  Lines       10761    10765    +4     
=======================================
+ Hits         9697     9701    +4     
  Misses       1064     1064           

Flag	Coverage Δ
total	90.12% <100.00%> (+<0.01%)	⬆️
unit	75.50% <100.00%> (+0.06%)	⬆️

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