Rewrite the core C++ type registration and FFI dispatch layer from
crates/bindings-cpp in Rust. The new crate provides:

- ModuleTypeRegistration: full SATS type registration with circular
  reference detection, error module generation, and BSATN serialization
- FFI dispatch: __describe_module__, __call_reducer__, __call_view__,
  __call_view_anon__, __call_procedure__ with proper Identity/ConnectionId
  reconstruction and BytesSource/BytesSink I/O
- Preinit functions: __preinit__01_clear_global_state and
  __preinit__99_validate_types matching the C++ originals

Replaces ~1,414 lines of C++ with ~1,139 lines of Rust (19% reduction)
plus 96 unit tests (100% coverage). Clippy-clean and fmt-clean.