[Feature]: Enable pure mode in devbox.json

[apgrucza]

Is your feature request related to a problem you're trying to solve? Please describe. Pure mode is a great step forward in providing more isolated Devbox environments, but currently it requires users to supply the --pure option when running devbox shell. Users may neglect to do this, resulting in inconsistent behaviour across users. The VS Code and direnv integrations also do not supply the --pure option.

Describe the solution you'd like If pure mode could be enabled in devbox.json, we can ensure Devbox environments will be consistent across all users. A benefit of this is that the VS Code and direnv integrations will support pure mode without requiring any changes.

Describe alternatives you've considered An alternative is that in a future version, pure mode becomes the default. In this case, pure mode would not need to be explicitly enabled indevbox.json.

[mohsenari]

Thanks for documenting this. Pure mode in devbox shell still has some rough edges as you know. We want to iterate on it as a flag for a couple of weeks to build confidence that its edge cases are covered before adding it to devbox.json.

[seven1m]

The --pure option has been really great for me. I'd love to make it the default!