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/cards/PlaylistCard.qml

@@ -57,6 +57,10 @@ import "../theme"
 
 Rectangle {
     id: root
+    readonly property bool artworkReady: root.artSource !== "" && artworkLoader.item
+        ? artworkLoader.item.ready : false
+    readonly property bool artworkImmediate: root.artSource !== "" && artworkLoader.item
+        ? artworkLoader.item.immediateGridArtwork : false
 
     property var item: ({})
     // Host-resolved artwork path (the AlbumCard artSource pattern).
@@ -194,12 +198,14 @@ Rectangle {
             // those surfaces pad too, and a genuinely square cover
             // (`image.covers[0]`, the fallback that map picks) still crops.
             Loader {
+                id: artworkLoader
                 anchors.fill: parent
                 sourceComponent: root.artSource !== "" ? singleArtwork : collageArtwork
             }
             Component {
                 id: singleArtwork
                 RoundedImage {
+                    gridArtwork: true
                     source: root.artSource
                     radius: theme.radiusSm
                     fit: root.ownImage ? "pad" : "auto"
@@ -211,6 +217,7 @@ Rectangle {
             Component {
                 id: collageArtwork
                 PlaylistCollage {
+                    gridArtwork: true
                     urls: root.ownImage ? [] : root.collageUrls
                     radius: theme.radiusSm
                 }