[libtaskmanager] Fix incorrect URL comparison when writing back a new launcher order

When computing the delta between the visible and the last saved launcher
order state, following the reordering of launchers, the code was incorrectly
comparing resolved and unresolved (i.e., for config storage) launcher URLs.
This lead to an incorrect result and therefore pinned tasks jumping around
in the Task Manager applet.

BUG:426880

libtaskmanager/tasksmodel.cpp

@@ -1773,7 +1773,17 @@ void TasksModel::syncLaunchers()
         for (int i = 0; i < rowCount(); ++i) {
             const QUrl &rowLauncherUrl = index(i, 0).data(AbstractTasksModel::LauncherUrlWithoutIcon).toUrl();
 
-            if (launcherUrlsMatch(launcherUrl, rowLauncherUrl, IgnoreQueryItems)) {
+            // `LauncherTasksModel::launcherList()` returns data in a format suitable for writing
+            // to persistent configuration storage, e.g. `preferred://browser`. We mean to compare
+            // this last "save state" to a higher, resolved URL representation to compute the delta
+            // so we need to move the unresolved URLs through `TaskTools::appDataFromUrl()` first.
+            // TODO: This bypasses an existing lookup cache for the resolved app data that exists
+            // in LauncherTasksModel. It's likely a good idea to eventually move these caches out
+            // of the various models and share them among users of `TaskTools::appDataFromUrl()`,
+            // and then also do resolution implicitly in `TaskTools::launcherUrlsMatch`, to speed
+            // things up slightly and make the models simpler (central cache eviction, ...).
+            if (launcherUrlsMatch(appDataFromUrl(launcherUrl).url,
+                rowLauncherUrl, IgnoreQueryItems)) {
                 row = i;
                 break;
             }