fix(qt): restore window lifecycle and improve grid artwork

Restore tray-aware close and quit confirmation, circular label covers, and missing label artist portraits. Publish artwork progressively, preload two grid rows, and skip redundant motion reports while preserving data refreshes.

Include regression tests and isolated artwork benchmarks. Verified Linux build, QML checks, and scrolling smoke tests.

cx

crates/qbz-qt/qml/controls/QbzConfirmModal.qml

@@ -58,6 +58,8 @@ Item {
     /// how a call site ends up setting a property that does not exist — which in
     /// QML is not an error, just a silently-ignored line.
     property bool danger: true
+    property string checkboxLabel: ""
+    property bool checkboxChecked: false
 
     readonly property bool opened: root._open
     property bool _open: false
@@ -184,6 +186,28 @@ Item {
                 font.pixelSize: root.kioskHost ? (theme.fontBody) * 1.2 : (theme.fontBody)
                 wrapMode: Text.WordWrap
             }
+            Row {
+                visible: root.checkboxLabel !== ""
+                width: parent.width
+                spacing: 10
+                QbzCheckbox {
+                    kioskHost: root.kioskHost
+                    checked: root.checkboxChecked
+                    Accessible.name: root.checkboxLabel
+                    onToggled: root.checkboxChecked = !root.checkboxChecked
+                }
+                Text {
+                    width: parent.width - 54
+                    text: root.checkboxLabel
+                    color: theme.textSecondary
+                    font.pixelSize: theme.fontBody
+                    wrapMode: Text.WordWrap
+                    MouseArea {
+                        anchors.fill: parent
+                        onClicked: root.checkboxChecked = !root.checkboxChecked
+                    }
+                }
+            }
             Item {
                 width: parent.width
                 height: root.kioskHost ? 44 : 36