Bug fix in last checkpoint save.#460

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chenyushuo wants to merge 2 commits intomodelscope:mainfrom

chenyushuo:fix/ckpt_save

Commits on Dec 30, 2025

Refactor checkpoint manager and add `latest_*_save_step` to avoid repeat save in same step
chenyushuo
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1. Enhance `TestTrainerCheckpointSave`
chenyushuo
committed