feat(qt): queue rows slide into place instead of the list being rebuilt

The Listen list and the sidebar queue now reach their views through
QbzKeyedModel. In the Listen list a removed track fades out while the
rows below slide up, "play next" slides the queue open, a history row
trimmed above the window leaves the rows on screen where they are, and a
committed drag lands the row where it was dropped while its neighbours
slide (the chevrons keep the animated swap). Identity is the track
(source + id, repeats by occurrence); phase, section and phaseIndex are
data, so a track ending updates rows in place and moves nothing. The
follow-playing position and the cover window now run after the model
holds the new rows. A search is a different list and is replaced at once.

The sidebar's Up Next and Recently played are Repeaters in Columns, which
have no remove transition: a leaving row disappears and the rows below
slide up, a joining row fades in, and a page or search change is laid out
synchronously without animation. Drop slots count the Repeater's own
items.

tst_keyed_model gains the Repeater-in-a-Column case (silent first page and
page change, sliding rows that keep their items, fading insert).

cc

crates/qbz-qt/qml/shell/QueuePanel.qml

@@ -38,6 +38,24 @@ Rectangle {
     readonly property var currentRow: doc.current || null
     readonly property var upcoming: doc.upcoming || []
     readonly property var historyRows: doc.history || []
+    // Keyed models for both lists (2026-09-14): a track leaving Up Next (it
+    // started playing, it was removed) disappears and the rows below slide up;
+    // a track joining slides the list open; nothing is rebuilt. The rows are
+    // Repeaters in a Column, so the motion is the Column's own add / move
+    // transitions — a positioner has no remove transition. Identity is the
+    // track (source + id, repeats by occurrence); another page or search
+    // replaces the list at once.
+    QbzKeyedModel {
+        id: upcomingModel
+        rows: root.upcoming
+        keyOf: function (row) { return (row.source || "") + ":" + row.id }
+        scope: JSON.stringify([root.doc.searchQuery || "", root.doc.page || 0])
+    }
+    QbzKeyedModel {
+        id: historyModel
+        rows: root.historyRows
+        keyOf: function (row) { return (row.source || "") + ":" + row.id }
+    }
     readonly property var settingsDoc: {
         try { return JSON.parse(QbzBridge.settingsJson) }
         catch (e) { return ({}) }
@@ -138,7 +156,8 @@ Rectangle {
     // arithmetic model to keep in sync. Top half of row k -> slot k, bottom
     // half -> slot k+1, past the last row -> N (append). <=40 rows per page.
     function slotFromPointer(winY) {
-        var n = root.upcoming.length
+        // The Repeater's own count: its items are what the pointer is over.
+        var n = upcomingRepeater.count
         for (var i = 0; i < n; i++) {
             var d = upcomingRepeater.itemAt(i)
             if (d && winY < d.rowCenterY())
@@ -223,7 +242,13 @@ Rectangle {
             root.coverMap = Object.assign({}, m)
         }
     }
-    Component.onCompleted: dispatchCovers()
+    Component.onCompleted: {
+        // The lists' Columns, laid out synchronously around a reset so a new
+        // page or search appears at once (QbzKeyedModel).
+        upcomingModel.views = [upNextSection]
+        historyModel.views = [historyBody]
+        dispatchCovers()
+    }
     onDocChanged: dispatchCovers()
     onQueueTrackArtworkChanged: dispatchCovers()
     // Collect the covers of the document CURRENTLY on the property and ask the
@@ -1026,13 +1051,18 @@ Rectangle {
                             font.letterSpacing: 0.5
                         }
 
+                        add: QbzRowAdd { enabled: upcomingModel.animate }
+                        move: QbzRowDisplaced { enabled: upcomingModel.animate }
+
                         Repeater {
                             id: upcomingRepeater
-                            model: root.upcoming
+                            model: upcomingModel
                             delegate: Column {
                                 id: upDelegate
-                                required property var modelData
+                                required property string rowKey
+                                required property int rowRev
                                 required property int index
+                                readonly property var modelData: upcomingModel.row(rowKey, rowRev)
                                 width: parent ? parent.width : 0
                                 // Row center in window space — slotFromPointer()
                                 // reads it off the Repeater's items.
@@ -1167,9 +1197,16 @@ Rectangle {
                         font.weight: theme.weightSemibold
                         font.letterSpacing: 0.5
                     }
+                    add: QbzRowAdd { enabled: historyModel.animate }
+                    move: QbzRowDisplaced { enabled: historyModel.animate }
+
                     Repeater {
-                        model: root.historyRows
+                        model: historyModel
                         delegate: QueueRow {
+                            required property string rowKey
+                            required property int rowRev
+                            required property int index
+                            readonly property var modelData: historyModel.row(rowKey, rowRev)
                             width: parent.width
                             row: modelData
                             rowIndex: index