Fix race condition in parallel UI status updates

Prevents stale, intermediate status messages from overwriting the final status of a completed task in the UI.

A set of completed task identifiers is now maintained. Any incoming intermediate status updates for tasks that are already marked as complete are ignored.

The job completion logic is also refactored for better robustness and clarity across different job-end states (failed, completed with data, completed without data).

FFUDevelopment/FFUUI.Core/FFUUI.Core.Shared.psm1

@@ -113,7 +113,16 @@ function Update-ListViewItemStatus {
     if ($WindowObject -is [System.Windows.Window] -and $ListView -is [System.Windows.Controls.ListView]) {
         # Directly update UI elements as this function is now called on the UI thread
         try {
-            $itemToUpdate = $ListView.ItemsSource | Where-Object { $_.$IdentifierProperty -eq $IdentifierValue } | Select-Object -First 1
+            # Determine which collection to search: ItemsSource (preferred) or Items.
+            $collectionToSearch = $null
+            if ($null -ne $ListView.ItemsSource) {
+                $collectionToSearch = $ListView.ItemsSource
+            }
+            else {
+                $collectionToSearch = $ListView.Items
+            }
+
+            $itemToUpdate = $collectionToSearch | Where-Object { $_.$IdentifierProperty -eq $IdentifierValue } | Select-Object -First 1
             if ($null -ne $itemToUpdate) {
                 $itemToUpdate.$StatusProperty = $StatusValue
                 $ListView.Items.Refresh() # Refresh the view to show the change