UI: Maintain more natural frame disposition when Console is in side bar

Currently if you place the Console in the side bar, it sometimes feels like a struggle to maintain the disposition. The default size of the side bar is about 25% and Positron often reverts to it. This happens sometimes on restart, though that may just be a dev setup thing. One thing I can consistently reproduce is making the side bar go back to its 25% default by double clicking on the vertical separator.

https://github.com/posit-dev/positron/assets/4465050/f79af2a2-f53e-47c1-9ee0-c59a224456e7

In my case it'd be more natural to use a default of 50% split when the Console is in the side bar. This may be because I'm using a 13inch screen though, users of larger screens might prefer to give more real estate to their editors. Ideally this would be configurable by the user, as a general setting or even better as settings specific to a particular disposition type (Console-in-Panel versus Console-in-Side-Bar).

Relevant discussion on the VSCode side: https://github.com/microsoft/vscode/issues/158603. In this issue users would like to configure and maintain different widths based on the selected view in the side bar. This seems relevant to us as well, if the user selects the Help view, the default width is too small for comfortable reading.

Based on this discussion, an alternative way of deciding the default width would be to say that whatever frame is holding the Console should have at a minimum a certain width (e.g. 40% or 50% by default).

Start by reproducing the Console-in-side-bar behavior, including double-clicking the vertical separator and restarting Positron. Read the linked VSCode discussion for related layout behavior and compare the possible width-configuration approaches. Done should mean the Console disposition remains usable and its width behavior is defined for the relevant layouts.