[zfergus]

Description

Fixes the Sphinx errors and warnings in the Python docs build, touching the pybind11 bindings and docs/source.

• Define CollisionMesh and ESPParameters before any signature that uses them, so pybind11 emits ipctk.CollisionMesh instead of the C++ name ipc::CollisionMesh, which the docs can't parse.
• Split define_esp_parameters out of define_esp_potential to allow that ordering.
• Give enum and object default arguments readable reprs via py::arg_v (e.g., TightInclusionCCD(), PSDProjectionMethod.NONE).
• Skip pybind11's internal base classes in autoclasstoc, which otherwise warns once per class.
• Escape |vertices| in docstrings and fix an RST underline length.

API changes

• None. Only the rendered default-argument reprs in Python signatures change.

Type of change

• This change requires a documentation update

How Has This Been Tested?

• Python docs build shows no new warnings

Checklist

• My code follows the clang-format style guidelines of this project