Name the monitor SCALE targets when multiple displays are connected

SCALE only applies to the focused monitor, which is easy to lose track
of with several displays. Show the focused monitor's name on the right
of the SCALE header (matching the BRIGHTNESS/TEXT SIZE value
convention), hidden when only one display is enabled.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

shell/plugins/panels/monitor/Panel.qml

@@ -714,10 +714,34 @@ Panel {
             width: parent.width
             spacing: Style.space(10)
 
-            PanelSectionHeader {
-              text: "SCALE"
-              foreground: root.bar.foreground
-              fontFamily: root.bar.fontFamily
+            Item {
+              width: parent.width
+              implicitHeight: Math.max(scaleHeader.implicitHeight, scaleMonitor.implicitHeight)
+
+              PanelSectionHeader {
+                id: scaleHeader
+                text: "SCALE"
+                foreground: root.bar.foreground
+                fontFamily: root.bar.fontFamily
+                anchors.left: parent.left
+                anchors.verticalCenter: parent.verticalCenter
+              }
+
+              // Name the monitor SCALE targets, since it only applies to the
+              // focused one.
+              Text {
+                id: scaleMonitor
+                text: root.focusedMonitor
+                // Only worth naming when more than one display is in play.
+                visible: root.focusedMonitor !== "" && root.enabledDisplayCount > 1
+                color: Qt.darker(root.bar.foreground, 1.4)
+                font.family: root.bar.fontFamily
+                font.pixelSize: Style.font.caption
+                font.bold: true
+                anchors.right: parent.right
+                anchors.rightMargin: Style.space(6)
+                anchors.verticalCenter: parent.verticalCenter
+              }
             }
 
             Grid {