Fix pt unit being misinterpreted as pints

[jmuhlich]

The OME schema defines "pt" as points but the pint default configuration makes it an alias for pints. This overrides the pt alias in our unit registry.

I added the option to ignore the override warning, also happy to discuss alternate approaches.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.85%. Comparing base (e4bda9e) to head (c1245f3).
Report is 8 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #271      +/-   ##
==========================================
+ Coverage   86.84%   86.85%   +0.01%     
==========================================
  Files          25       25              
  Lines        1262     1263       +1     
==========================================
+ Hits         1096     1097       +1     
  Misses        166      166              

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[codspeed-hq]

CodSpeed Performance Report

Merging #271 will improve performances by 11.98%

_{Comparing jmuhlich:units-pt-is-point (c1245f3) with main (e4bda9e)}

Summary

⚡ 1 improvements
✅ 8 untouched benchmarks

Benchmarks breakdown

	Benchmark	main	jmuhlich:units-pt-is-point	Change
⚡	test_time_from_xml[large]	3.3 s	3 s	+11.98%