Screens: a reset button next to the grab bar, clickable in VR games

Each desktop screen gets a reset button left of its bar (a reticle). It
puts every screen back in its layout around where you are now, like
Meta+Shift+R (ft-layout apply).

In a VR game the screens leave the controllers to the game (the
outside_games and dashboard modes), so a controller couldn't click any
of their controls. Aiming a hand controller at the reset button now sets
MakeOverlaysInteractiveIfVisible on that button's overlay alone, so the
trigger clicks it; the flag clears half a second after the aim leaves a
zone twice as wide, and the game gets the controllers back. The aim
comes from the laser poses ft-screens already reads to show the controls.

The ft-layout spawn is now RunLayout(cmd), shared with the arrange.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/design.md

@@ -62,6 +62,8 @@ A profile's screen part is the custom arrangement under a name: each screen's po
 
 `IVRApplications::GetCurrentSceneProcessId()` is 0 when no game is running (the Frame's home environment isn't a scene app) and the game's process ID while one is. ft-screens checks it twice a second, turns the flag off while a game runs, and by default hides the screens unless the dashboard is open. Flatscreen games run inside Steam's gamescope overlay and aren't scene apps, which is why "only with the dashboard open" is offered as a controller setting.
 
+The reset button needs to work in a game, where the screens have the flag off. So ft-screens turns the flag on for that button's overlay alone while a hand controller aims within about one button's width of it, and off half a second after the aim leaves a zone twice as wide. ft-screens finds the aim from the controllers' laser poses, which it reads anyway to show the controls, so it doesn't need SteamVR's laser to be on first. The game loses the controllers only while you aim at the button.
+
 ## Floating windows
 
 [floating-windows.md](floating-windows.md) describes the feature and its parts. Drag and drop and the clipboard only work between windows of one compositor, so a floating window stays a KWin window and gets a KWin output of its own: one of the spare outputs KWin opens after the screens, shown by ft-screens as a panel cropped to the window. What follows is how KWin 6.2.5 behaves underneath that, from its source (`src/backends/wayland/`) and from trying it on the Frametop desktop.