Review everything shipped this weekend, and fix what the reviewers caught

Claude-Session: https://claude.ai/code/session_01Ms2FbjQy31TVf3CEvQhGM8

config/dot/quickshell/modules/dock/DockBody.qml

@@ -248,13 +248,34 @@ Rectangle {
     // are their own surface: leaving the icon to reach them would otherwise
     // close the thing being reached for.
     property Item previewAnchor: null
-    property var previewApp: null
+
+    // Looked up in the live model rather than snapshotted when the dwell fires.
+    // `items` is rebuilt into fresh objects whenever any window opens or
+    // closes, so a snapshot keeps the window list the app had when the pointer
+    // stopped moving: a window closed while its preview is up stays in the
+    // strip, and its ScreencopyView goes on holding a handle to a surface that
+    // no longer exists. Reading it back out of `items` means the strip empties
+    // itself, and an app whose last window closed drops the preview entirely.
+    readonly property var previewApp: {
+        const anchor = root.previewAnchor;
+        if (!anchor || !anchor.app)
+            return null;
+        const id = anchor.app.appId;
+        for (let i = 0; i < root.items.length; i++) {
+            if (root.items[i].appId === id)
+                return root.items[i];
+        }
+        return null;
+    }
 
     // Written by the Dock from the preview popup's own hover.
     property bool previewHovered: false
 
     onHoveredItemChanged: root.reconsiderPreview()
     onPreviewHoveredChanged: root.reconsiderPreview()
+    // A window opening or closing changes what the strip should be showing --
+    // including, when it was the last one, whether there should be a strip.
+    onItemsChanged: root.reconsiderPreview()
 
     function reconsiderPreview(): void {
         const item = root.hoveredItem;
@@ -277,7 +298,6 @@ Rectangle {
         previewDwell.stop();
         previewGrace.stop();
         root.previewAnchor = null;
-        root.previewApp = null;
         root.previewHovered = false;
     }
 
@@ -289,7 +309,6 @@ Rectangle {
             if (!item || !item.app || !item.app.windows || item.app.windows.length === 0)
                 return;
             root.previewAnchor = item;
-            root.previewApp = item.app;
         }
     }
 
@@ -375,6 +394,13 @@ Rectangle {
                 onDragMoved: travel => root.moveDrag(travel)
                 onDragEnded: root.endDrag()
                 onDragCancelled: root.cancelDrag()
+
+                // Keying the model keeps a delegate alive through a rebuild,
+                // but not through the app's last window closing while it is
+                // being dragged: that row is gone, and the release it owed is
+                // gone with it. Without this the dock keeps dragIndex forever,
+                // which reads as a dock that will not hide again.
+                Component.onDestruction: if (root.dragIndex === dockItem.index) root.cancelDrag()
             }
         }
     }