Handle URDF multidof joint limits

[jslee02]

Apply URDF multi-DOF joint limits and parsing fixes.

• Parses planar/floating URDF joint limits uniformly across DOFs with warnings; derives planar plane from .
• Adds regression tests for planar/floating URDF limits and documents the semantics.
• Closes URDF Multidimensional Joint Limits #327.

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Before creating a pull request

• Run pixi run test-all to lint, build, and test your changes (relied on GitHub CI)
• Add unit tests for new functionality
• Document new methods and classes
• Add Python bindings (dartpy) if applicable

[codecov]

Codecov Report

❌ Patch coverage is 83.60656% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 60.90%. Comparing base (5237903) to head (7e726aa).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
dart/utils/urdf/DartLoader.cpp	83.60%	10 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2233      +/-   ##
==========================================
+ Coverage   60.82%   60.90%   +0.07%     
==========================================
  Files         353      353              
  Lines       31880    31940      +60     
  Branches     4128     4139      +11     
==========================================
+ Hits        19392    19453      +61     
+ Misses      12488    12487       -1     

Flag	Coverage Δ
unittests	60.90% <83.60%> (+0.07%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
dart/dynamics/GenericJoint.hpp	100.00% <ø> (ø)
dart/dynamics/detail/GenericJoint.hpp	75.69% <ø> (ø)
dart/utils/urdf/DartLoader.cpp	83.19% <83.60%> (+4.55%)	⬆️

... and 1 file with indirect coverage changes

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