I want erys to support opening and saving Jupyter notebook files through its terminal app.

I want erys to support opening and saving Jupyter notebook files through its terminal app.: a task in MiMo-V2.6-RL-harbor-code: MiMo-V2.6-RL Code (Harbor) (Harbor dataset). When the app saves a notebook to a path, it should write valid JSON to that path with top-level metadata , nbformat …

The task

When the app saves a notebook to a path, it should write valid JSON to that path with top-level `metadata`, `nbformat`, `nbformat_minor`, and `cells` fields. The saved metadata should include `kernel_info`, `kernel_spec`, and `language_info`, and the `cells` array should contain one entry for each current notebook…

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