Native Leiden community detection for [sdivi-rust](https://github.com/geoffgodwin/sdivi-rust).
Pure Rust port of the Leiden algorithm (Traag et al. 2019, Modularity + CPM quality function).
No FFI, no C++ dependency — deterministic across platforms with a seeded `StdRng`.
Part of the `sdivi-rust` workspace. See the [workspace README](../../README.md) for full documentation.