Add new GitHub Actions workflow for Copilot environment setup

[shachafl]

This pull request updates the way Copilot's environment setup steps are managed by removing the previous .github/copilot-setup-steps.yml configuration file and replacing it with a new GitHub Actions workflow .github/workflows/copilot-setup-steps.yml. The new workflow leverages GitHub Actions to automate and validate the setup process, ensuring consistency and enabling easier testing.

Key changes:

Migration to GitHub Actions workflow:

• Removed the standalone .github/copilot-setup-steps.yml file, which previously documented and scripted the environment setup steps for Copilot, including system dependencies, Python version management, and supported Makefile targets.
• Added a new .github/workflows/copilot-setup-steps.yml workflow that:
  • Defines a reusable, matrix-based workflow to test setup on Python 3.10 and 3.13.
  • Automates code checkout, Python environment setup, dependency installation, linting, type checking, and running fast tests.
  • Triggers on workflow dispatch, and on changes to the workflow file itself via push or pull request events.

Simplification and automation:

• The new workflow consolidates environment setup, dependency installation, and basic validation (linting, type checking, and tests) into a single, easily maintainable CI workflow.
• The previous manual documentation and step-wise scripting are now handled by standardized GitHub Actions, reducing duplication and improving reliability.

Overall, this change modernizes and streamlines the Copilot setup process by leveraging GitHub Actions for automation and validation.