fix: [#63] Add Jupyter notebook (.ipynb) support to edit tool

[nandanosql]

Fixes #63

Problem

The edit/view tools cannot handle .ipynb (Jupyter notebook) files. When the agent tries to view or edit a notebook, it either shows raw JSON or fails because the file contains complex structured data.

Solution

Added special handling for .ipynb files in TextEditorTool:

View command

• Detects .ipynb files and parses the JSON notebook format
• Displays each cell with a header showing cell type (code/markdown) and index
• Shows cell source content in a readable format

str_replace command

• Converts all cell sources to a flat text representation with cell marker comments (# %% Cell N (type))
• Applies string replacement on this representation
• Reconstructs the notebook JSON from the modified text, preserving cell structure
• Supports the same uniqueness check as regular files

Changes

• Added json import
• Added _is_notebook(), _read_notebook(), _write_notebook() helpers
• Added _notebook_cells_to_text() for view rendering
• Added _notebook_to_source_text() for str_replace editing
• Added _apply_str_replace_to_notebook() and _reconstruct_notebook_from_text()
• Modified _view() to detect and render notebooks
• Modified _str_replace_handler() to handle notebooks
• Updated tool description to mention notebook support

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