Re-format CLI instructions to use sphinx-tabs for three different OSes

https://github.com/djungelorm/sphinx-tabs

This same approach can be used other places where we have diverging instructions based on platform, but doing it with CLI commands throughout the contributor technical guide would be the best first place.

Start with the contributor technical guide and locate its CLI command instructions. Review the linked sphinx-tabs approach, then reformat the guide's platform-divergent instructions for the three operating systems; done means the guide presents those commands in tabs and remains clear to contributors.

Written by the indexing model from the issue text.