Switch from Nox to Tox for multi-version Python testing

[tkoyama010]

Summary

This PR replaces Nox with Tox for test automation, providing support for multiple Python versions.

Changes

• Add tox.ini with support for Python 3.10, 3.11, and 3.12
• Define test environments:
  • py310, py311, py312 - Run tests with pytest
  • docs - Build documentation with Sphinx
  • lint - Run pre-commit hooks
• Remove noxfile.py
• Update GitHub Actions workflow to use tox

Usage

Run all tests:

tox

Run specific Python version:

tox -e py311

Build docs:

tox -e docs

Run linting:

tox -e lint

Benefits

• Better multi-version Python testing support
• Standard tool widely used in the Python ecosystem
• Isolated test environments per Python version
• Easy to integrate with CI/CD pipelines

[Copilot]

Pull request overview

This PR migrates the project's test automation from Nox to Tox, maintaining support for Python 3.10, 3.11, and 3.12 (dropping 3.9 support, which is consistent with the project's existing requires-python = '>=3.10' requirement in pyproject.toml).

Changes:

• Adds tox.ini configuration with test, docs, and lint environments
• Removes noxfile.py
• Updates GitHub Actions workflow to use tox with tox-gh-actions plugin

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
tox.ini	New tox configuration file defining test environments for Python 3.10-3.12, plus docs and lint environments
noxfile.py	Removed nox configuration that previously supported Python 3.9-3.12
.github/workflows/testing-and-deployment.yml	Updated to install and run tox instead of directly installing test dependencies and running pytest

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