nx_hygiene_prims.nx

nx_hygiene_prims.nx -- foundational primitives for the NISHI_CODE_HYGIENE_STANDARD.md (nishi-silicon commit f4cc144). Provides the building blocks new code MUST use to satisfy hygiene classes M1 (null safety), M2 (overflow safety), M4 (alloc safety), M5 (index safety). Once this ships, every commit going forward starts born-clean per the §4.1 MUST set. WINNER-TIER: WINNER-A (preserves the cardinal); paired with the standards docs that establish the bar INCUMBENTS: Rust std::option::Option, Rust checked_arithmetic, Ada SPARK contracts, MISRA C INT30-C rule, CERT INT32-C, libstd's bounds-checked indexer NUMBERS: V1 ships the primitives; benchmark vs Rust's checked_mul + alloc + Option pending paired bench GAP: Rust's Option<T> is language-built-in; this is a substrate-level convention. Future M3 milestone lifts NxOpt into a language-level type. PLAN: M-next: per-file remediation using these primitives; ratchet metric tracks count of null-creation + unchecked-alloc + raw-multiply sites going down per commit EXEMPTION REASON: n/a; provisional pending measurement Status: SEED v0.1.0. 2026-05-27.