Default to light mode in Jupyter notebooks

[emilk]

Jupyter notebooks always have a light background. I therefor want Rerun to default to light mode there (and in other “bright” notebook surroundings).

But I otherwise want Rerun to respect the system preferences by default (both on web and on native).

[Wumpf]

@emilk I saw you and @jprochazk discussing this on Slack. Was there any conclusion on whether this can be done?

[jprochazk]

We don't yet know how to do this reliably. We can treat it as another "UI property" like panel states, and expose an option in the Viewer constructor for it.

But also light mode isn't done yet:

• Perfecting light mode design #10107

[emilk]

To explain: Rerun does respect the theme preference of the system, but Jupyter doesn't:

So the question becomes: Do we care? And if we do, should we try to follow the theme of the "surroundings" rather than the whole system?