Make notifications legible, and follow windows that ask for focus

The notification background was a 6% foreground tint over a transparent
window, which meant it had nothing behind it at all: the card sat
directly on whatever was on screen and the text competed with it.
Notifications are the one surface someone reads without having chosen to
look at it, so it now uses a real popover surface -- a little lighter
than one you opened deliberately, because a toast arrives unbidden and
full popover weight reads as a dialog demanding an answer.

Windows that ask for attention are now switched to rather than merely
highlighted, so a link opening on another workspace takes you there.
That setting already existed and was simply off; it is a preference
rather than a hardcoded behaviour, so it can be turned back off on the
Desktop & Dock page.

Claude-Session: https://claude.ai/code/session_01BRvzt4H8XXLPVH5MyYdk9L

config/dot/quickshell/modules/notifications/NotificationCard.qml

@@ -35,7 +35,17 @@ Rectangle {
     implicitHeight: Math.max(layout.implicitHeight + 24, image.visible ? 96 : 0)
     radius: Theme.cardRadius
     border.width: 0
-    color: hover.containsMouse ? Theme.alpha(Theme.fg, 0.1) : Theme.alpha(Theme.fg, 0.06)
+    // A real popover surface, the same one the date menu and clipboard panel
+    // use, rather than a 6% foreground tint.
+    //
+    // A tint that faint has nothing behind it: the toast window is transparent,
+    // so the card was sitting directly on whatever happened to be on screen and
+    // the text competed with it. Notifications are the one surface someone reads
+    // without having chosen to look at it, so it has to be legible over a
+    // bright photo and a white document alike.
+    color: hover.containsMouse
+        ? Theme.alpha(Theme.mix(Theme.bgPopover, Theme.fg, 0.06), Theme.toastAlpha)
+        : Theme.alpha(Theme.bgPopover, Theme.toastAlpha)
 
     Behavior on color {
         ColorAnimation {