eval_jacobi and eval_legendre

[jorenham]

For either integral/real $n$ and real/complex $z$. For integral $n$ and real $z$, this is implemented in pure-Rust (by me). Otherwise, it wraps hyp2f1 from xsf, exactly like it's done in SciPy.

Towards #144

[Copilot]

Pull Request Overview

This PR adds support for evaluating orthogonal polynomials (Jacobi and Legendre) by translating the relevant scipy.special functions to Rust. The implementation follows the project structure by providing pure Rust translations from the scipy.special Cython code with trait-based function overloading for real and complex types.

• Adds eval_jacobi and eval_legendre functions for evaluating Jacobi and Legendre polynomials at a point
• Implements sealed trait pattern for supporting both f64 and Complex64 types with i32 and f64 degree parameters
• Includes comprehensive test coverage with manual test cases and scipy-derived expected values

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
src/scipy_special/orthogonal_eval.rs	New module implementing Jacobi and Legendre polynomial evaluation functions with trait-based dispatch for different types
src/scipy_special/mod.rs	Adds orthogonal_eval module and exports eval_jacobi and eval_legendre functions
src/lib.rs	Updates crate-level documentation to include new orthogonal polynomials section