v0.4.0

Release Notes

This release adds Python 3.14 support and brings significant improvements to both the
Rust core and the Python API. Key highlights include a corrected second derivative
formula, proper handling of mixed LineString/LinearRing inputs, and better error
handling by returning Result instead of panicking. On the Rust side, two crate
dependencies (lazy_static and num_cpus) have been removed in favor of standard
library alternatives, and all major dependencies have been bumped. The Python API gains
__repr__ and __slots__ on CatmullRom, along with cleaner data passing to Rust by
using plain lists instead of numpy array intermediaries.

Added

• Python 3.14 support.
• __repr__ method on CatmullRom class for better debugging output.
• __slots__ on CatmullRom class for reduced memory usage and prevention of dynamic
  attribute creation.
• Length validation in linestrings_tangent_angles to raise an error when
  gaussian_sigmas length does not match the number of input lines.
• grid property in _catsmoothing.pyi type stubs.

Fixed

• Fixed second derivative formula in spline evaluation (was constant 6.0 instead of
  correct 6.0 * t).
• In smooth_linestrings, if the input was a mix of LineString and LinearRing the
  output was either a LineString or a LinearRing depending on the type of the
  first input. Now, the output correctly is a mix of LineString and LinearRing
  depending on the type of each element in the input.
• Fixed _catsmoothing.pyi type stubs to match the actual Rust API signatures.
• Removed outdated scipy requirement mention from smooth_polygon docstring.

Changed

• evaluate() and uniform_distances() now return Result instead of panicking on
  invalid input, propagating errors to Python as ValueError.
• Replaced lazy_static with std::sync::LazyLock and num_cpus with
  std::thread::available_parallelism(), removing two crate dependencies.
• Enforce valid polygon generation in smooth_polygon using shapely.make_valid
  function.
• Vec2D now derives Copy for reduced heap allocations.
• Improved spline evaluation by using partition_point for binary search and ordered
  tangent construction instead of insert(0, ...).
• Pass bc_types as a plain list[str] to Rust instead of converting through a numpy
  string array.
• Pass gaussian_sigmas as a plain list in linestrings_tangent_angles instead of
  converting through a numpy array.
• Bumped Rust dependencies: ndarray 0.16 to 0.17, pyo3 0.24 to 0.28, numpy (crate)
  to 0.28, rand to 0.10, rand_distr to 0.6.