v2.2.1 — tag, manifest and crate agree, and the clamp is cross-language-proven

Cargo.toml and Cargo.lock carry 2.2.1, so the tag, the manifest and the crate say the same version. The compressed-float range clamp carries cross-language witnesses: the wire-compatibility gate pins the C++ reference at v1.14.0 and proves the clamped values byte-identical across the boundary. STANDARD.md is re-synced with upstream, including the corrected contraction-suppression guidance and the writer-fusion vector band.