Edit Jupyter notebook (.ipynb) files. Supports inserting, deleting, and replacing cells.

Operations:
- insert: Add a new cell at the specified index
- delete: Remove the cell at the specified index
- replace: Replace the content of the cell at the specified index

Cell types: "code", "markdown", "raw"

For insert and replace operations, provide the cell content. The notebook structure (metadata, outputs, execution counts) is preserved.