Add focused window controls to top bar

Introduces a new `WindowControls` component in the desktop top bar with minimize, maximize/restore, and close actions for the focused window. `WindowService` now exposes focused-window presence/maximized state plus focused-window convenience actions to support this UI.

Also extends Nebula UI with a reusable `NebulaToolTip`, keyboard/pressed-state support in `NebulaIconButton`, new window-control glyphs in `NebulaIcon`, and theme tokens for pressed/danger hover states, with CMake and README updates to register/document the new components.

shells/desktop/shell/CMakeLists.txt

@@ -48,6 +48,7 @@ set(NEBULA_SHELL_QML_FILES
     qml/surfaces/TopBarSurface.qml
     qml/surfaces/LauncherSurface.qml
     qml/components/TopBar.qml
+    qml/components/WindowControls.qml
     qml/components/NebulaButton.qml
     qml/components/Clock.qml
     qml/components/SystemArea.qml

shells/desktop/shell/qml/components/TopBar.qml

@@ -23,15 +23,19 @@ Item {
         id: left
         anchors.left: parent.left
         anchors.leftMargin: 6
+        anchors.right: right.left
+        anchors.rightMargin: 12
         anchors.verticalCenter: parent.verticalCenter
         spacing: 8
 
         NebulaButton {
+            id: nebulaButton
             checked: ShellState.launcherOpen
             onClicked: ShellState.toggleLauncher()
         }
 
         Rectangle {
+            id: leftDivider
             anchors.verticalCenter: parent.verticalCenter
             width: 1
             height: 14
@@ -40,7 +44,7 @@ Item {
 
         Text {
             anchors.verticalCenter: parent.verticalCenter
-            width: Math.min(implicitWidth, root.width * 0.4)
+            width: Math.min(implicitWidth, Math.max(0, left.width - nebulaButton.width - leftDivider.width - left.spacing * 2))
             text: ShellState.activeApplication
             color: Theme.textSecondary
             font.family: Theme.fontFamily
@@ -50,9 +54,28 @@ Item {
         }
     }
 
-    SystemArea {
+    Row {
+        id: right
         anchors.right: parent.right
         anchors.rightMargin: 10
         anchors.verticalCenter: parent.verticalCenter
+        spacing: windowControls.visible ? 8 : 0
+
+        WindowControls {
+            id: windowControls
+            anchors.verticalCenter: parent.verticalCenter
+        }
+
+        Rectangle {
+            visible: windowControls.visible
+            width: visible ? 1 : 0
+            height: 14
+            color: Theme.borderStrong
+            anchors.verticalCenter: parent.verticalCenter
+        }
+
+        SystemArea {
+            anchors.verticalCenter: parent.verticalCenter
+        }
     }
 }

shells/desktop/shell/qml/components/WindowControls.qml

@@ -0,0 +1,76 @@
+import QtQuick
+import Nebula.UI
+import Nebula.Windows
+
+Item {
+    id: root
+
+    readonly property bool maximized: WindowService.focusedWindowMaximized
+
+    visible: WindowService.hasFocusedWindow
+    implicitWidth: well.implicitWidth
+    implicitHeight: Theme.controlHeight
+    width: visible ? implicitWidth : 0
+    Accessible.role: Accessible.Grouping
+    Accessible.name: qsTr("Window controls")
+
+    Rectangle {
+        id: well
+        anchors.fill: parent
+        implicitWidth: row.implicitWidth + 2
+        implicitHeight: Theme.controlHeight
+        radius: Theme.radiusSmall
+        color: Theme.iconWell
+        border.width: 1
+        border.color: Theme.border
+
+        Row {
+            id: row
+            anchors.centerIn: parent
+            spacing: 0
+
+            NebulaIconButton {
+                id: minimizeButton
+                width: 26
+                height: 26
+                label: qsTr("Minimise")
+                onClicked: WindowService.minimizeFocusedWindow()
+
+                NebulaIcon {
+                    name: "minimize"
+                    size: 14
+                    color: minimizeButton.iconColor
+                }
+            }
+
+            NebulaIconButton {
+                id: maximizeButton
+                width: 26
+                height: 26
+                label: root.maximized ? qsTr("Restore") : qsTr("Maximise")
+                onClicked: WindowService.toggleMaximizeFocusedWindow()
+
+                NebulaIcon {
+                    name: root.maximized ? "restore" : "maximize"
+                    size: 14
+                    color: maximizeButton.iconColor
+                }
+            }
+
+            NebulaIconButton {
+                id: closeButton
+                width: 26
+                height: 26
+                label: qsTr("Close")
+                danger: true
+                onClicked: WindowService.closeFocusedWindow()
+
+                NebulaIcon {
+                    name: "close"
+                    size: 14
+                    color: closeButton.iconColor
+                }
+            }
+        }
+    }
+}