Async example wrong

Async example wrong: a task in MiMo-V2.6-RL-harbor-code: MiMo-V2.6-RL Code (Harbor) (Harbor dataset). BUG Async example wrong Seems like session for validator creates only on aenter

The task

[BUG] Async example wrong Seems like session for validator creates only on `__aenter__`

Part of FineEnvs/MiMo-V2.6-RL-harbor-code.