oms-modbus 0.2.0

[Preview] High-performance, transport-generic Modbus library. Full Master (client) and Slave (server) for TCP, RTU, ASCII — unified API, passive bus monitoring, spec-compliant timing.
Documentation
## Description

<!-- Briefly describe what this PR does. -->

## Type of change

- [ ] Bug fix
- [ ] New feature
- [ ] Breaking change (public API)
- [ ] Documentation / examples
- [ ] Performance improvement
- [ ] Test coverage

## Checklist

- [ ] `cargo fmt --check` passes
- [ ] `cargo clippy --all-targets -- -D warnings` passes
- [ ] `cargo test` passes (all test suites)
- [ ] New functionality has tests
- [ ] Public API changes are documented
- [ ] No `.unwrap()` added to production code