feat: "Start Steam silently" sub-option for the SteamOS conversion (silent) and Gaming on NVIDIA (nvsilent)

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

ui/qml/Texts.qml

@@ -10,12 +10,18 @@ QtObject {
         boot: { label: "Boot into", hint: "Where the PC starts",
                 body: "Where the PC starts after a restart. Switching back and forth works the same either way.",
                 changes: ["Desktop: the Plasma session is set before login", "Gaming: the SteamOS default"] },
+        silent: { label: "Start Steam silently", hint: "In the tray at login on the desktop, no window",
+                  body: "Steam starts by itself when you log in to the Plasma desktop, in the tray without a window. Gaming mode starts its own Steam.",
+                  changes: ["Steam is started with -silent (a systemd user service, desktop only)", "Off: the service is removed again"] },
         nvidia: { label: "Gaming on NVIDIA", hint: "Steam on the desktop, started at login",
                   body: "gamescope's own gaming mode shows a corrupted picture on NVIDIA graphics cards (an open NVIDIA driver bug), so it isn't offered here. This puts Steam on the Plasma desktop instead and starts it when you log in.",
                   changes: ["Steam is installed when it's missing", "Steam starts at login (a systemd user service)", "Off: the service is removed again; Steam is only removed if Steamify installed it"] },
         bigpicture: { label: "Steam starts in Big Picture", hint: "The controller-friendly Steam, or the normal window",
                       body: "Steam opens in Big Picture at login, which works well with a controller on the TV. Untick it for Steam's normal window.",
                       changes: ["Steam is started with -gamepadui", "Plasma starts with an empty session, so old windows don't cover Big Picture", "Off: Steam starts in its normal window"] },
+        nvsilent: { label: "Start Steam silently", hint: "In the tray at login, no window",
+                    body: "Steam starts in the tray at login without a window. Not together with Big Picture: ticking one unticks the other.",
+                    changes: ["Steam is started with -silent", "Off: Steam starts in its normal window"] },
         theme: { label: "SteamOS theme", hint: "Vapor look for the desktop, Add to Steam",
                  body: "The Vapor look of SteamOS for the desktop, with its panel, launcher icon and wallpaper.",
                  changes: ["cachyos-vapor global theme", "Add to Steam in right-click menus", "Nested Desktop, Steam keyboard window rule"] },