Skore UI / Activity feed: Smaller layout and thoughtful information display

[GaelVaroquaux]

Is your feature request related to a problem? Please describe.

We should prioritize the information displayed on skore UI to:

1. Make a good use of screen real estate
2. Help the user see more easily what's important for his work (following the "less is more" paradigm)

This is important because, as I work on my laptop screen, I struggle to find space to put the activity feed window (see screenshot):

It is also important to help me focus on the important stuff, and avoid an information overload feeling

Describe the solution you'd like

While what I feel is important is to have a general thought about the way information is laid out and space is used, we can see a few things that can probably be improved from the above screenshot:

• Activity feed

  • We have a lot of empty vertical bars (spacer) on the left and the right. These are good when we are in a wide window, but if I want to put the activity feed as a fraction of the screen (which is how it feels natural for me), these end up using a lot of my available space
  • the bar on the left with the skore logo and the selectors should probably be collapsed when the screen is narrow

• Display of the CrossValidationReporter

  • It seems that there is twice the same value reported, the one that has as a value "0.90". That's not very good from a UX perspective, it's confusing as I'm left wondering what the difference between the two is. Making the window wider shows that one is called "Mean test r2" and the second one is called "Mean test score". I'm pretty sure that they are the same thing. I should not have two different names for the same thing

  • Should the value of each fold be displayed by default? From an application perspective, I'm not sure that this is meaningful. IMHO it should be collapsed.

  • More generally, we need to think about what the messages that we want the user to crasp quickly from such a display, and optimize the display to convey these messages. The question is then: what is the user going to want of this display? I suspect, an appreciation of the multiple ways a model performs, as well as the variability and reliability of the corresponding measures.

  • Moving to the "plots", I have the same questions:

    • The information about what differs across the bars is in a tiny space (almost all bars have the same height)
    • Is the difference between the bars important? What am I supposed to conclude from this plot?
    • the y axis is "value", that's a fairly generic name. I need to see at a glance what it means
      
    • clicking on the legend, I can overlay "test_score" and "test_r2", but I believe that these are actually the same values
    • I can also overlay "test_root_mean_squared_error" with "test_r2", but it has no meaning to overlay those two on the same y axis, as they have completely different scales
      

Describe alternatives you've considered, if relevant

No response

Additional context

No response