Add validated identifiers, Hash32, Timestamp and DataClass to proto

Implemented-By: Laguna S 2.1 (OpenCode)

crates/proto/src/lib.rs

@@ -1 +1,7 @@
 //! Shared data types and the frame codec for Boxmaker. No policy and no I/O beyond frames.
+
+pub mod class;
+pub mod ids;
+
+pub use class::DataClass;
+pub use ids::{CallId, Epoch, Hash32, SessionId, Timestamp, ValueError};