feat: add notebook watcher with auto-conversion to markdown

[jxnl]

Summary

• Added a notebook watcher script that monitors Jupyter notebooks and automatically converts them to markdown format
• Helps with version control and documentation by maintaining markdown versions of notebooks

Changes

• New watch_notebooks.py script: Monitors .ipynb files and converts on save
• Updated convert.py: Added file command for single file conversion
• Added dependencies: typer, watchdog, rich, nbformat for the watcher functionality
• Updated README: Added documentation for the notebook watcher tool

Features

• Automatically converts all existing notebooks on startup
• Watches for changes and converts modified notebooks in real-time
• Saves markdown files to md/ directory by default (configurable)
• Beautiful console output with progress indicators using Rich
• CLI interface with help and options using Typer

Usage

# Watch current directory
./watch_notebooks.py

# Watch specific directory
./watch_notebooks.py /path/to/notebooks

# Custom output directory  
./watch_notebooks.py -o /custom/output

🤖 Generated with Claude Code

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Important

Adds a notebook watcher script to automatically convert Jupyter notebooks to markdown for improved version control and documentation.

• New Features:
  • Adds watch_notebooks.py to monitor .ipynb files and convert them to markdown on save.
  • Automatically converts all existing notebooks on startup and watches for real-time changes.
  • Saves markdown files to md/ directory by default, configurable via CLI.
• Updates to convert.py:
  • Adds file command to convert a single notebook to markdown.
• Dependencies:
  • Adds typer, watchdog, rich, nbformat to pyproject.toml for watcher functionality.
• Documentation:
  • Updates README.md with usage instructions for the notebook watcher tool.

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[ellipsis-dev]

Using relative_to(notebook_path.parent) may raise a ValueError if the output directory is not a subdirectory of the notebook's directory; consider displaying the output path more safely.

Suggested change

	console.print(f"[green]✓[/green] Converted [blue]{notebook_path.name}[/blue] → [green]{output_path.relative_to(notebook_path.parent)}[/green]")
	console.print(f"[green]✓[/green] Converted [blue]{notebook_path.name}[/blue] → [green]{output_path}[/green]")

[ellipsis-dev]

The subprocess call block is duplicated; consider refactoring to a helper function to DRY up the code.