LayerShell windows with non-spanning anchors (AnchorTop|AnchorRight)
crash the compositor when made invisible because Qt briefly resizes
the surface to 0 before unmapping it. Wrap GamingHUD in a Loader so
the window is destroyed rather than hidden.
Replace the generic 'Yes / Cancel' exit dialog with 'Keep Playing /
Leave' in both the Game Center header and the QS tile, matching the
mental model of a couch user.
The 'Launch Hint' QS tile is now hidden (available: false) when
gaming mode is off so it does not clutter the regular action drawer.
Full-screen layer-shell overlay containing a game library grid
(XDG Game category, filtered via ApplicationListSearchModel) and
a panel of running tasks built on TaskManager.TasksModel.
Keyboard-navigable with directional focus between the running
tasks row and the game grid. A persistent HUD button lets the
user return after launching a game. Exiting gaming mode requires
an explicit confirmation dialog.
The overlay is a Window with LayerShell.LayerTop so it sits above
running application windows without covering system notifications.
