BiorthBasis: use Eigen::Ref for getAccel inputs

[lgarrison]

In Gala, we have raw pointers and want to call the array overload for getAccel, so we're using Eigen::Map like so:

  Eigen::Map<Eigen::VectorXd> eigen_x(q.x, N);
  Eigen::Map<Eigen::VectorXd> eigen_y(q.y, N);
  Eigen::Map<Eigen::VectorXd> eigen_z(q.z, N);

  auto& allaccel = exp_state->basis->getAccel(eigen_x, eigen_y, eigen_z);

This currently doesn't work because the getAccel args must be VectorXd, not Map. This PR changes the API to accept Maps by changing the input types to Eigen::Ref<const Eigen::VectorXd>.

[The9Cat]

Thanks. That looks right to me. I'll do a quick check on an existing notebook that tests getAccel, and then merge if there are no issues. Don't expect that there will be.

[Copilot]

Pull Request Overview

This PR updates the getAccel method signatures in the BiorthBasis class to use Eigen::Ref<const T> instead of non-const references, improving API flexibility and const-correctness. The changes allow these methods to accept a wider variety of Eigen types while properly indicating that the input parameters are not modified.

• Changed parameter types from Eigen::VectorXd& to Eigen::Ref<const Eigen::VectorXd> for vector overloads
• Changed parameter type from RowMatrixXd& to Eigen::Ref<const RowMatrixXd> for matrix overload
• Updated Python bindings to match the new C++ signatures

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
expui/BiorthBasis.H	Updated getAccel method signatures to use Eigen::Ref<const T> parameters for improved const-correctness and flexibility
pyEXP/BasisWrappers.cc	Updated Python binding py::overload_cast templates to match the new C++ method signatures

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[The9Cat]

My checks all work as expected. Merging...