Retype distortion models to SpectralPositionalVectorArray

[roytsmart]

Summary

Changes the optika.distortion model I/O from optika.vectors.SceneVectorArray to na.SpectralPositionalVectorArray, so scene and sensor coordinates share a single named-arrays vector type.

• AbstractDistortionModel.distort/undistort now take and return na.SpectralPositionalVectorArray (abstract return type na.AbstractSpectralPositionalVectorArray); coordinates_sensor stays Cartesian2dVectorArray.
• PolynomialDistortionModel.fit feeds coordinates_scene directly into PolynomialFitFunctionArray (the scene vector already exposes wavelength/position.x/position.y as polynomial components), and undistort returns a SpectralPositionalVectorArray.

Motivation

ctis (which sits above optika, like esis) implements the same scene→sensor forward model in ctis.instruments.IdealInstrument and already uses na.SpectralPositionalVectorArray for both scene and sensor coordinates. Standardizing optika's distortion model on the same named-arrays type lets ctis and optika.systems.AbstractInterpolatedSystem reuse these models without repackaging coordinates between SceneVectorArray and SpectralPositionalVectorArray.

Testing

• pytest optika/distortion/_distortion_test.py — 26 passed (distort/undistort/round-trip, fit, and plot_residual across degree ∈ {1, 2}).
• 100% coverage on the module; black --check and ruff check clean.

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.29%. Comparing base (2a2fe34) to head (35087f4).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #156      +/-   ##
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- Coverage   99.29%   99.29%   -0.01%     
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  Files         111      111              
  Lines        5537     5533       -4     
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- Hits         5498     5494       -4     
  Misses         39       39              

Flag	Coverage Δ
unittests	99.29% <100.00%> (-0.01%)	⬇️

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