[WIP] Update README.md with exercise descriptions

[Copilot]

• Create .github/workflows/update_readme.yml - GitHub Actions workflow that triggers on push
• Create .github/scripts/update_readme.py - Python script that:
  • Scans all .ipynb files in the repo
  • Extracts brief descriptions (max 3 lines) from notebook comments/markdown cells
  • Organizes exercises by folder name and file name
  • Updates README.md (creates or updates the Exercises section)
  • Handles updates to pre-existing notebooks
• Verify the workflow and script work correctly

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