.NETpad 2025: Settings Auto Flow (Premium)

Looking over the to-do list for .NETpad in 2025, I decided to start small and make one of the easier changes to the app first. That change? Settings auto-flow.
What to do, what to do
I realized after posting .NETpad 2025: What Comes Next (Premium) that I had left out some of the known issues I noted in Modernizing .NETpad: New App Version is Now Available on GitHub (Premium) and on the project's GitHub page. So I combined the two lists into a single to-do list in Notion. Which looks like so:
.NETpad 2025 to-do
[ ] Remove App theme button when Microsoft fixes WPF bug

[ ] Add Snap layout flyout support to Maximize window button

[ ] Disable document actions (Open, Save, etc.) when viewing app settings

[ ] Prevent custom dialog resize

[ ] Prevent black selection rectangles from appearing app-wide

[ ] App session state
[ ] One document
[ ] Two documents
[ ] Any number of documents
[ ] Settings layout auto-flow per Notepad

[ ] App window minimum heights and widths

[ ] Tabs
[ ] Tab item header customization in C#
[ ] Add tab button w/proper layout
[ ] Two tabs
[ ] Any number of tabs w/proper layout and overflow solution
[ ] Autocorrect per Notepad

[ ] AI-powered Rewrite per Notepad

Some of these are in progress and some are for the future, but it's nice to make progress, so I started thinking about which of these items could be completed quickly. And settings layout auto-flow seemed like the easiest.
Settings layout auto-flow
If you look at the settings interface in Notepad, you can see that there's a single layout auto-flow effect. If the app window is thin enough, all the content appears in a single column. But if you resize it to be wide enough, the bottom block of content, "About this app," reflows into a second column on the right.

.NETpad doesn't do this. No matter how wide the app window is, all the settings content appears in a single column.
Testing the change
To test an auto-flow update, I created a new Visual Studio project and roughed out some simple XAML with a grid with two rows and two columns, each with a colored button. By default, the two buttons appear on top of each other in the same column.

Then, I created a SizeChanged() event handler for the app window and researched how to change the grid row and column assignments for the two buttons. Then, I picked an arbitrary width and changed the values accordingly. If the window is 1000 or fewer device-independent pixels (DIPs) wide, the buttons will appear above each other in a single column. If it's wider, they will appear side-by-side in two columns.

That seemed to work fine, but the reflow effect happened a bit abruptly, and I assumed that Notepad used a simple animation of some kind to address that.

But in looking at Notepad, I noticed that wasn't the case. It looks/works exactly like the example I had created. So there was no need to go down that rabbit hole.
Implementing it in .NETpad
I was pretty excited...