Assistant papercuts NC34

[marcoambrosini]

A few papercuts and possible improvements I found while reviewing recent changes, feel free to pick up what you can and/or create sub issues from any of the points.

• Increase minimum width for displaying the history to 900px.
• Change generic hamburger icon to toggle sidebar into a history icon when the navigation is closed. Move the new into the main content. Right aligned in the top bar.
• Increase default width of the dialog. Currently it's set at 50% which is unnecessarily narrow on laptop screens. Even if we have a new draggable window we should try to maintain the sizing logic we had for the old dialog (at least for the initial size)