fix: respect multi-axis pos_attr when segmentation is present

[TeunHuijben]

When pos_attr was passed as a list (e.g. ['z', 'y', 'x']) to Tracks/SolutionTracks alongside segmentation data, the user-specified position key was silently ignored. Two bugs caused this:

• _get_feature_set() only handled pos_attr inside an if self.segmentation is None block, so multi-axis positions were never registered when segmentation was present.
• _setup_core_computed_features() unconditionally overwrote features.position_key with the RegionpropsAnnotator default ("pos"), discarding any value set earlier.

Fix: move multi-axis pos_attr handling outside the segmentation guard (since those columns are always static/pre-existing on nodes), and guard the annotator assignment with if self.features.position_key is None

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.96%. Comparing base (055f446) to head (ea3747e).
⚠️ Report is 7 commits behind head on v2-dev.

Additional details and impacted files

@@           Coverage Diff           @@
##           v2-dev     #188   +/-   ##
=======================================
  Coverage   92.96%   92.96%           
=======================================
  Files          59       59           
  Lines        3268     3269    +1     
=======================================
+ Hits         3038     3039    +1     
  Misses        230      230           

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[cmalinmayor]

Is this a problem on main too?

[TeunHuijben]

I think it is, but only surfaces when I was loading external graphs that had x/y/z/pos columns and I didn't want to use the pos column