//! Phase R6: retired. See `integrated_trainer_smoke.rs`.
//!
//! The flawed Phase F+G `MockLobEnv` toy-bandit convergence-gate test
//! that used to live here has been retired per the "no toys" feedback
//! that drove the rebuild. Its core check — "the trainer's gradient
//! signal reaches the PPO policy head" — is now covered structurally
//! by the GPU-resident kernel tests (R3, R4, R5) and end-to-end by
//! `integrated_trainer_smoke.rs` (real `LobSimCuda`, one GPU-pure
//! `step_with_lobsim` call, asserts finite losses).
//!
//! File preserved (empty) so the rename history is preserved.
