fix(constitution): use per-joint anchor positions in spherical joint simplified API

[Ligo04]

Summary

• Fix variable shadowing bug in the simplified apply_to overload where vector<Vector3> r_local_pos redefined the parameter Vector3 r_local_pos, causing a compilation error.
• Change simplified API to accept span<Vector3> r_local_pos (per-joint anchor positions) instead of a single Vector3, giving callers more flexibility while keeping the uniform strength_ratio scalar.
• Update pybind binding to match: the simplified overload now takes a numpy array of anchor positions (py::array_t<Float>) converted via as_span_of<Vector3>.
• Update test case (80_abd_spherical_joint) to use the new simplified API.

Changed Files

File	Change
include/uipc/constitution/affine_body_spherical_joint.h	Add span<Vector3> r_local_pos param to simplified overload
src/constitution/affine_body_spherical_joint.cpp	Fix shadowing, accept span<Vector3>
src/pybind/pyuipc/constitution/affine_body_spherical_joint.cpp	Update pybind to pass py::array_t<Float> → span<Vector3>
apps/tests/sim_case/80_abd_spherical_joint.cpp	Use simplified API with per-joint anchors

[gemini-code-assist]

Code Review

This pull request updates the AffineBodySphericalJoint::apply_to API to support per-joint anchor positions by adding a new r_local_pos parameter. These changes are propagated through the C++ implementation, test cases, and Python bindings. The review feedback suggests renaming several parameters (such as l_instance_id and strength_ratio) to their plural forms in both the C++ and Python signatures to ensure naming consistency across the codebase.

[gemini-code-assist]

For consistency with the simplified apply_to overload and general C++ best practices, it's recommended to use plural names for parameters that are collections (like span).

Consider renaming the following parameters in this function signature (and its declaration in the header file) to reflect that they are collections:

• l_instance_id -> l_instance_ids
• r_instance_id -> r_instance_ids
• strength_ratio -> strength_ratios

This will improve readability and consistency across the API.

Suggested change

	span<IndexT> l_instance_id,
	span<IndexT> l_instance_ids,

[gemini-code-assist]

For consistency and to improve readability, it's better to use plural names for parameters that are collections, like py::array_t. This makes the Python API more intuitive.

Please consider renaming l_instance_id, r_instance_id, and strength_ratio to their plural forms. Remember to also update their usage inside the lambda body.

Suggested change

	py::array_t<IndexT> l_instance_id,
	py::list r_geo_slots,
	py::array_t<IndexT> r_instance_id,
	py::array_t<Float> r_local_pos,
	py::array_t<Float> strength_ratio)
	py::array_t<IndexT> l_instance_ids,
	py::list r_geo_slots,
	py::array_t<IndexT> r_instance_ids,
	py::array_t<Float> r_local_pos,
	py::array_t<Float> strength_ratios)