feat(qt): Shift ranges in the library folders settings table

A row or checkbox click toggled one folder. Shift now adds the run over the
rows the filter shows, Ctrl adds one, and the ids stay numbers for the
removal action.

cc

crates/qbz-qt/qml/settings/LibraryFolderTable.qml

@@ -42,10 +42,23 @@ Column {
         })
     }
     function isSelected(id) { return selectedIds.indexOf(id) >= 0 }
-    function toggleSelected(id) {
-        const next = selectedIds.slice()
-        const at = next.indexOf(id)
-        if (at >= 0) next.splice(at, 1); else next.push(id)
+    /// A plain or Ctrl click toggles one folder; Shift adds the range from the
+    /// last plain click over the rows SHOWN (the filter is a view filter) —
+    /// the rule every multi-select list shares (controls/SelectionModel.qml).
+    SelectionModel { id: folderSel }
+    function toggleSelected(id, mods) {
+        const rows = root.shown()
+        const current = {}
+        for (let i = 0; i < selectedIds.length; i++)
+            current[String(selectedIds[i])] = true
+        const picked = folderSel.next(current, id, rows,
+                                      mods === undefined ? Qt.NoModifier : mods)
+        // Back to the ids themselves (the removal action takes them as
+        // numbers), keeping earlier picks the filter currently hides.
+        const next = selectedIds.filter(function (sid) { return picked[String(sid)] === true })
+        for (let j = 0; j < rows.length; j++)
+            if (picked[String(rows[j].id)] === true && next.indexOf(rows[j].id) < 0)
+                next.push(rows[j].id)
         selectedIds = next
     }
     function scanLabel(ts) {
@@ -118,6 +131,7 @@ Column {
                     QbzBridge.settingsString("library-remove-folders",
                         JSON.stringify(root.selectedIds))
                     root.selectedIds = []
+                    folderSel.anchorId = ""
                 }
             }
         }
@@ -279,7 +293,9 @@ Column {
                 anchors.fill: parent
                 hoverEnabled: true
                 cursorShape: Qt.PointingHandCursor
-                onClicked: root.toggleSelected(folderRow.modelData.id)
+                onClicked: function (mouse) {
+                    root.toggleSelected(folderRow.modelData.id, mouse.modifiers)
+                }
             }
 
             Row {
@@ -292,7 +308,9 @@ Column {
                     width: root.kioskHost ? 44 : 20
                     anchors.verticalCenter: parent.verticalCenter
                     checked: root.isSelected(folderRow.modelData.id)
-                    onToggled: root.toggleSelected(folderRow.modelData.id)
+                    onToggled: function (mods) {
+                        root.toggleSelected(folderRow.modelData.id, mods)
+                    }
                 }
                 // FOLDER: type glyph + name.
                 Row {