Refine window chrome position and sizing

Updates UI theme metrics for traffic-light controls and chrome inset to slightly larger values. In the desktop window chrome surface, positioning now uses the title bar center directly, rounds rendered margins, and introduces short easing animations for X/Y chrome offsets to reduce jitter during movement.

packages/nebula-ui/qml/Nebula/UI/Theme.qml

@@ -52,9 +52,9 @@ QtObject {
     readonly property int topBarHeight: 40
     readonly property int controlHeight: 28
     readonly property int searchHeight: 36
-    readonly property int trafficLightSize: 18
+    readonly property int trafficLightSize: 20
-    readonly property int trafficLightGap: 8
+    readonly property int trafficLightGap: 9
-    readonly property int windowChromeInset: 12
+    readonly property int windowChromeInset: 14
 
     readonly property int fontSize: 13
     readonly property int fontSizeApp: 12

shells/desktop/shell/qml/surfaces/WindowChromeSurface.qml

@@ -14,9 +14,10 @@ Window {
     readonly property int chromeY: {
         const barY = WindowService.focusedWindowTitleBarY
         const barH = Math.max(WindowService.focusedWindowTitleBarHeight, height)
-        const centered = barY + Math.round((barH - height) / 2)
+        return barY + Math.round((barH - height) / 2)
-        return centered - Theme.topBarHeight
     }
+    property real renderedChromeX: chromeX
+    property real renderedChromeY: chromeY
 
     title: qsTr("Nebula Window Chrome")
     color: "transparent"
@@ -28,11 +29,25 @@ Window {
     LayerShell.Window.scope: "nebula-window-chrome"
     LayerShell.Window.layer: LayerShell.Window.LayerTop
     LayerShell.Window.anchors: LayerShell.Window.AnchorLeft | LayerShell.Window.AnchorTop
-    LayerShell.Window.margins.left: Math.max(0, chromeX)
+    LayerShell.Window.margins.left: Math.max(0, Math.round(renderedChromeX))
-    LayerShell.Window.margins.top: Math.max(0, chromeY)
+    LayerShell.Window.margins.top: Math.max(0, Math.round(renderedChromeY))
     LayerShell.Window.exclusionZone: 0
     LayerShell.Window.keyboardInteractivity: LayerShell.Window.KeyboardInteractivityNone
 
+    Behavior on renderedChromeX {
+        NumberAnimation {
+            duration: 34
+            easing.type: Easing.OutQuad
+        }
+    }
+
+    Behavior on renderedChromeY {
+        NumberAnimation {
+            duration: 34
+            easing.type: Easing.OutQuad
+        }
+    }
+
     WindowControls {
         id: controls
         anchors.centerIn: parent