- Introduce `MaxDepthBehavior` option (`Throw`, `Truncate`, `Disable`) for explicit depth-limit handling in AcBinarySerializer and SGen.
- Default is now `Throw` (fail-fast); `ShallowCopy` preset uses `Truncate` for shallow-copy semantics.
- Refactor runtime and SGen paths to use unified `TryEnterRecursion`/`ExitRecursion` for correct wire output and inc/dec symmetry.
- Add focused tests to diagnose SGen+Truncate wire-misalignment bug (see `BINARY_ISSUES.md#accore-bin-i-t7k3`).
- Update docs and comments to clarify new behavior and document Toon serializer's current lack of `MaxDepthBehavior` support.
- Adjust tests and usages for new semantics and improved safety.
