fix(ComboBox): fix highlight lingering after mouse leaves

- Track the popup's hover state by adding a contentHovered property,
and modify the highlighted property in the delegate.
- The logic of the highlighted property now depends on
contentHovered, automatically clearing the highlight when the
mouse leaves.

修复鼠标移出后高亮项仍然残留的问题

- 通过添加contentHovered属性跟踪popup悬停状态，修改delegate的highlighted
- 属性逻辑依赖contentHovered，鼠标离开时自动清除高亮

Log: 修复ComboBox的菜单项鼠标离开后高亮残留问题
Influence: ComboBox菜单项
PMS: BUG-304991

Author: electricface

qt6/src/qml/ComboBox.qml

@@ -36,7 +36,7 @@ T.ComboBox {
         useIndicatorPadding: true
         text: control.textRole ? (Array.isArray(control.model) ? modelData[control.textRole] : (model[control.textRole] === undefined ? modelData[control.textRole] : model[control.textRole])) : modelData
         icon.name: (control.iconNameRole && model[control.iconNameRole] !== undefined) ? model[control.iconNameRole] : null
-        highlighted: control.highlightedIndex === index
+        highlighted: popup.contentHovered ? control.highlightedIndex === index : false
         hoverEnabled: control.hoverEnabled
         autoExclusive: true
         checked: control.currentIndex === index
@@ -169,13 +169,24 @@ T.ComboBox {
         rightMargin: DS.Style.popup.margin
         palette: control.palette
         implicitWidth: control.flat ? Math.max(contentItem.implicitWidth, control.width) : control.width
+        property bool contentHovered: false
+        Connections {
+            target: control
+            function onHighlightedIndexChanged() {
+                if (control.highlightedIndex >= 0)
+                    popup.contentHovered = true
+            }
+        }
         contentItem: ArrowListView {
             clip: true
             maxVisibleItems: control.maxVisibleItems
             view.model: control.delegateModel
             view.currentIndex: control.highlightedIndex
             view.highlightRangeMode: ListView.ApplyRange
             view.highlightMoveDuration: 0
+            HoverHandler {
+                onHoveredChanged: popup.contentHovered = hovered
+            }
         }
 
         background: FloatingPanel {