feat: add tests for notebooks

[gemmadanks]

What changes did you make (give an overview)?

• Added tests for notebooks
• Fixed bug in example notebook
• Added just command for starting Jupyter from the devcontainer
• Updated documentation

Prerequisites checklist

Please check each of the following before merging:

• This pull request is ready to merge (leave unchecked to indicate a WIP)
• I will squash my commits and, where needed, edit the commit messages to make them more informative and follow the conventional commits format
• I have updated relevant documentation
• I have linked to relevant issues
• I have created an ADR (Architectural Decision Record) for architecturally significant changes

What is the purpose of this pull request?

Check all that apply:

• Documentation update
• Changes to dependencies
• Refactor
• Improved tests
• Improved CI
• Bug fix
• Changes to an existing feature
• New feature
• Other, please explain:

[Copilot]

Pull request overview

This PR adds comprehensive testing support for Jupyter notebooks in the project. It fixes an import bug in the example notebook, adds infrastructure for running notebook tests using nbmake, and improves developer experience with new just commands and updated documentation.

Key Changes:

• Added nbmake dependency and test command for automated notebook testing
• Fixed incorrect function import in the example notebook (greet → say_hello)
• Added Jupyter lab command for running notebooks in devcontainers

Reviewed changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated no comments.

File	Description
pyproject.toml	Added nbmake dependency for notebook testing
notebooks/example.ipynb	Fixed function import bug and corrected cell type for markdown heading
justfile	Added test-notebooks and jupyter-devcontainer commands
README.md	Updated documentation with new test command and fixed package rename instruction

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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