First public release since forking from Twinklebear/embree-rs. Safe Rust
bindings to Embree 3.13.5 that turn the raw FFI into a memory-safe API.

Highlights:
- Safe FFI layer: heap-owned callback closures via a lock-free per-geometry
  table; GeometryBuilder/Geometry typestate; non-Clone Scene (share via
  Arc<Scene>); typed zero-copy buffers.
- Standalone BVH builder (Device::create_bvh / Bvh::build_scoped).
- Scene-vs-scene collision (Scene::collide).
- Packet ray queries with a typed, aligned ValidMaskN, ergonomic per-lane
  iteration (for_each_active_lane), and per-ray context extensions.

Pre-1.0: the API may change between minor releases and some Embree functions
are not yet wrapped. See CHANGELOG.md.