chore: add #![forbid(unsafe_code)] to safe Rust crates

Adds the forbid(unsafe_code) crate-level attribute to all Rust crates
that do not use unsafe code, hardening the safety guarantee at compile
time.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: hyperpolymath

src/main.rs

@@ -17,6 +17,7 @@
 //! 4. **Diff Compression**: Reduces dataset size by storing only the residual 
 //!    between original and VAE-decoded images.
 
+#![forbid(unsafe_code)]
 mod metadata;
 
 use anyhow::{Context, Result, bail};