feat: support flattened CBOR extension maps Add #[serde(flatten)] support for map-shaped #[derive(Cbor)] structs and preserve integer COSE labels through CBOR round trips. Add cbor encode --hex and cbor validate for agent-friendly CLI workflows. Bump cbor2 crates to 1.0.5 and switch project metadata and docs to MIT-only licensing. Co-Authored-By: Anda Bot <noreply@anda.bot>