Sandbox the execution environments for Python and Ruby subcommands

[artob]

Use case

We should not rely on nor require having an up-to-date, correctly-installed, and correctly-configured Python or Ruby system environment.

Proposal

We should execute external subcommands implemented using Python with a Python 3 toolchain & venv rooted in $HOME/.asimov/envs/python. Possible mechanisms: mise, uv, RustPython

We should execute external subcommands implemented using Ruby with a Ruby 3 toolchain rooted in $HOME/.asimov/envs/ruby. Possible mechanisms: mise, Artichoke