Summary

• Add 16 new C API functions exposing Manifold and MeshGL/MeshGL64
  methods that had no C binding:
  • manifold_get_tolerance, manifold_set_tolerance, manifold_simplify,
    manifold_num_prop_vert
  • manifold_meshgl{,64}_tolerance, _run_flags_length, _run_flags,
    _num_run, _update_normals
• Add thread safety note to the C header: objects are not safe for concurrent
  access, even read-only, due to lazy evaluation with mutable internal state.
• Add tests for all new bindings.

Motivation

These gaps were found while building manifold-csg,
a new Rust FFI binding to the C API. Missing accessors for runFlags, tolerance,
NumRun, and UpdateNormals prevent lossless round-tripping of MeshGL data.
GetTolerance/SetTolerance/Simplify are useful public Manifold methods
with no C-side equivalent (manifold_epsilon exists but calls the GetEpsilon
testing hook rather than the public GetTolerance).

The thread safety note documents the mutable shared_ptr lazy-evaluation
pattern in Manifold and CrossSection, which is relevant for FFI consumers
that need to decide whether concurrent read access is safe (it isn't).

Test plan

• All 15 CBIND tests pass (4 new: tolerance, num_prop_vert,
  meshgl_run_accessors, meshgl_update_normals)
• No changes to existing tests or behavior

🤖 Generated with Claude Code