//! Allocation-free error topology.
//!
//! The canonical `SolverError` set for boundary rejection and fail-safe conditions: no heap allocation, no `Display` by default, byte-size budgeted.
//!
//! Defined by RFC 003 (Allocation-Free Error Topology) and RFC 014 (status/error split). Lands in Milestone 1; this Phase 0 placeholder declares no public
//! items yet.
