Addition of copy with separator button/keystroke

It would be really useful to have a copy with separator button in Solveit. That way I could copy a cell or groups of cells from solveit and paste them into jupyter notebook and later reload that notebook in solveit. My use case is working with large datasets that I have to work on locally. I want to use solveit to develop techniques and interact with AI but inevitably not all cells will be able to run in solveit directly. Therefore using a hybrid of local jupyter and remote solveit is helpful. I can currently save and open complete ipynb files between the two platforms. If I can copy paste with separators intact I could copy relevent additions to my jupyter notebook without having to reload the notebook and rerun everything. Finally on saving the ipynb in jupyter it could be reloaded into solveit again and separators would be intact - so the relevent ai dialog would be maintained.
I'm posting here as directed by the discord !ask buddy

No implementation file or test is named in the issue. Start by locating Solveit's current cell copy/paste and ipynb import/export entry points, then establish the separator-preserving button or keystroke behavior and verify that copied cells can round-trip through Jupyter without losing the AI dialog.

Written by the indexing model from the issue text.