100% Rust typed handle-addressed store — Region<T> + generational Handle<T> + thread-safe SyncRegion<T> over the audited `slotmap` crate. The single-threaded face of sefer-alloc, extracted as a standalone crate: zero own unsafe (#![forbid(unsafe_code)]), no C/C++ libraries pulled in, no_std + alloc capable. For users who want a typed slotmap-like handle store WITHOUT pulling a full allocator stack.