//! Storage-agnostic vector and matrix access contracts.
//!
//! Shape queries, fallible indexing, mutable access, and borrowed-view compatibility — no heavy linear-algebra kernels and no storage-layout commitment.
//!
//! Defined by RFC 002 (Storage-Agnostic Matrix and Vector Access Contracts). Lands in Milestone 1; this Phase 0 placeholder declares no public
//! items yet.
