Apps are not windows: Don't group windows by application (in the tiling popup)

Briefly describe how the feature should work

Instead of grouping windows by application in the tiling popup, I propose showing all windows ungrouped (along with a window preview) as long as the window list is short enough.

In case we need to handle too many windows to fit on the screen, the view could still become scrollable. If the windows are sorted by a heuristic for their relevance (e. g. "recently used", like in the [alt]+[tab] pop-up), this would ensure that the most relevant windows would still easily be accessible.

Explain why this feature should be added

• you can tile windows, but you can't tile applications
• less clicks to select a window when other windows of the same app are open
• all windows could have window previews
• applications are a very technical and complicated concept. Imagine you write a document and you want to tile a source to one side. Depending on the source file format, it might be open in a different application, and depending on what else you have open, there might be multiple windows rendered by that application. This is stuff you don't want to think about just to tile a window.

Explaining why 2 files are shown in 2 different groups currently basically requires explaining file formats, the idea of programs being needed to paint the file contents on screen, and file format support of programs. This is complicated and technical stuff if you think about it.

The issue names no files, tests, or entry points. Start by locating the tiling popup implementation and its window-grouping behavior; review how it currently selects and displays windows. Done should mean that short window lists can show individual windows with previews, while longer lists remain usable through scrolling or relevance-based ordering.