fix(ui): normalize TreeView expanded keys to strings for sessionStorage compatibility

Keys from KeySelector (e.g. boxed int) were compared against string keys
restored from sessionStorage, causing expansion state to be lost on
navigation. All keys are now normalized to strings internally.

src/ScadaLink.CentralUI/Components/Shared/TreeView.razor

@@ -32,7 +32,7 @@ else
         var key = KeySelector(item);
         var children = ChildrenSelector(item);
         var isBranch = HasChildrenSelector(item);
-        var isExpanded = _expandedKeys.Contains(key);
+        var isExpanded = _expandedKeys.Contains(KeyStr(key));
 
         <li role="treeitem" @key="key"
             aria-expanded="@(isBranch ? (isExpanded ? "true" : "false") : null)"
@@ -66,7 +66,10 @@ else
 
 @code {
     private IReadOnlyList<TItem>? _items;
-    private HashSet<object> _expandedKeys = new();
+    private HashSet<string> _expandedKeys = new();
+
+    /// <summary>Normalize any key object to a string for consistent comparison with sessionStorage.</summary>
+    private string KeyStr(object key) => key.ToString()!;
     private bool _initialExpansionApplied;
     private bool _storageLoaded;
     private TItem? _contextMenuItem;
@@ -124,7 +127,7 @@ else
                 var keys = System.Text.Json.JsonSerializer.Deserialize<List<string>>(json);
                 if (keys != null)
                 {
-                    _expandedKeys = new HashSet<object>(keys);
+                    _expandedKeys = new HashSet<string>(keys);
                     _initialExpansionApplied = true;
                 }
             }
@@ -159,7 +162,7 @@ else
         {
             if (InitiallyExpanded!(item))
             {
-                _expandedKeys.Add(KeySelector(item));
+                _expandedKeys.Add(KeyStr(KeySelector(item)));
             }
 
             var children = ChildrenSelector(item);
@@ -172,9 +175,10 @@ else
 
     private void ToggleExpand(object key)
     {
-        if (!_expandedKeys.Remove(key))
+        var k = KeyStr(key);
+        if (!_expandedKeys.Remove(k))
         {
-            _expandedKeys.Add(key);
+            _expandedKeys.Add(k);
         }
 
         PersistExpandedState();
@@ -184,8 +188,7 @@ else
     {
         if (StorageKey != null)
         {
-            var keys = _expandedKeys.Select(k => k.ToString()!).ToList();
+            var json = System.Text.Json.JsonSerializer.Serialize(_expandedKeys.ToList());
-            var json = System.Text.Json.JsonSerializer.Serialize(keys);
             _ = JSRuntime.InvokeVoidAsync("treeviewStorage.save", StorageKey, json);
         }
     }
@@ -232,7 +235,7 @@ else
         {
             if (HasChildrenSelector(item))
             {
-                _expandedKeys.Add(KeySelector(item));
+                _expandedKeys.Add(KeyStr(KeySelector(item)));
             }
 
             var children = ChildrenSelector(item);
@@ -258,13 +261,14 @@ else
     public async Task RevealNode(object key, bool select = false)
     {
         var parentLookup = BuildParentLookup();
+        var k = KeyStr(key);
 
         // If key is not in the tree at all, no-op
-        if (!parentLookup.ContainsKey(key))
+        if (!parentLookup.ContainsKey(k))
             return;
 
         // Walk up through ancestors
-        var current = key;
+        var current = k;
         while (parentLookup.TryGetValue(current, out var parentKey) && parentKey != null)
         {
             _expandedKeys.Add(parentKey);
@@ -280,9 +284,9 @@ else
         StateHasChanged();
     }
 
-    private Dictionary<object, object?> BuildParentLookup()
+    private Dictionary<string, string?> BuildParentLookup()
     {
-        var lookup = new Dictionary<object, object?>();
+        var lookup = new Dictionary<string, string?>();
         if (_items is { Count: > 0 })
         {
             BuildParentLookupRecursive(_items, null, lookup);
@@ -290,11 +294,11 @@ else
         return lookup;
     }
 
-    private void BuildParentLookupRecursive(IReadOnlyList<TItem> items, object? parentKey, Dictionary<object, object?> lookup)
+    private void BuildParentLookupRecursive(IReadOnlyList<TItem> items, string? parentKey, Dictionary<string, string?> lookup)
     {
         foreach (var item in items)
         {
-            var key = KeySelector(item);
+            var key = KeyStr(KeySelector(item));
             lookup[key] = parentKey;
 
             var children = ChildrenSelector(item);