Bug fixes to anatomical workflow

[kaitj]

A couple of small bug fixes for the anatomical workflow (tested and confirmed working locally e2e).

1. Updated fslmaths call - I think this changed in the most recent niwrap version
2. Updated composite transform paths (was previously passing the object instead of the file path)

Tests coming in separate PR.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 29.50%. Comparing base (56dfd40) to head (a0435ba).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/rbc/core/anatomical/registration.py	0.00%	1 Missing ⚠️

❌ Your project status has failed because the head coverage (29.50%) is below the target coverage (80.00%). You can increase the head coverage or adjust the target coverage.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #40   +/-   ##
=======================================
  Coverage   29.50%   29.50%           
=======================================
  Files           7        7           
  Lines          61       61           
=======================================
  Hits           18       18           
  Misses         43       43           

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[nx10]

Looks good - we should switch from simplenamespace to namedtuples or dataclasses in subsequent PRs. Dynamic class creation isn't needed here.

[kaitj]

Yah, lets chat more about that offline.

I originally had it as a dataclass, but its really only used here to return paths in a single "object" once, wasn't sure it made sense and also the immutability of the namedtuples, but definitely open to it.