Add compute_sinuosity kinematics metric

[mujju-212]

Summary

• add compute_sinuosity to movement.kinematics.kinematics
• export compute_sinuosity from the public movement.kinematics API
• add focused unit tests for straight, curved, stationary, and too-short trajectories

Details

Sinuosity is implemented as:

• path length over selected time range (compute_path_length)
• divided by straight-line start-end distance (compute_norm(end - start))

Behavior:

• supports the same
  an_policy options as compute_path_length (fill, scale)
• supports start / stop slicing in time units
• returns NaN when straight-line distance is zero (undefined ratio)

Testing

• pytest -q -k sinuosity tests/test_unit/test_kinematics/test_kinematics.py

Closes #904

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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