//! Unified control backend contract — split into trait definition and mock implementations.
//!
//! This module is split from the original monolithic `trait_def.rs` (1730 lines, BLUE11 R9.1):
//! - `trait_def.rs` — the `ControlBackend` trait definition only
//! - `mock.rs` — test mock (`TestBackend`) and associated unit tests
// BLUE11: Allow module inception; `trait_def` is the trait definition sub-module
// inside `trait_def/` parent directory.
pub use ControlBackend;