//! Space trait - marker for spatial structures in which agents exist.
/// Marker trait for simulation spaces.
///
/// Spaces define the topology in which agents live (grid, continuous, graph, etc.).
/// Concrete space types live in the `rustsim-spaces` crate and implement both this
/// trait and [`SpaceInteraction`] for positioned agent types.
///
/// The `Send + Sync` bounds allow spaces to be shared across threads when needed
/// by the compute backend.
///
/// [`SpaceInteraction`]: crate::interaction::SpaceInteraction