fix(ui): enforce idempotent AI data fetching and JSRuntime guards

src/NexusReader.UI.Shared/Components/Molecules/AiAssistantBubble.razor

@@ -51,9 +51,13 @@
     private string _lastFetchedBlockId = string.Empty;
     private KnowledgePacket? _packet;
     private CancellationTokenSource? _streamCts;
+    private bool _isInteractive;
 
     protected override async Task OnParametersSetAsync()
     {
+        if (!_isInteractive)
+            return;
+
         // Only re-fetch when the block context actually changes
         if (string.IsNullOrEmpty(ContextBlockId) || ContextBlockId == _lastFetchedBlockId)
             return;
@@ -62,6 +66,19 @@
         await FetchAndStreamAsync();
     }
 
+    protected override async Task OnAfterRenderAsync(bool firstRender)
+    {
+        if (firstRender)
+        {
+            _isInteractive = true;
+            if (!string.IsNullOrEmpty(ContextBlockId))
+            {
+                _lastFetchedBlockId = ContextBlockId;
+                await FetchAndStreamAsync();
+            }
+        }
+    }
+
     private async Task FetchAndStreamAsync()
     {
         // Cancel any in-progress stream

src/NexusReader.UI.Shared/Components/Molecules/GroundednessBadge.razor

@@ -26,15 +26,40 @@
 
     private GroundednessResult? _result;
     private bool _isChecking;
+    private bool _isInteractive;
+    private string _previousAnswer = string.Empty;
+    private string _previousContext = string.Empty;
+
+    protected override void OnParametersSet()
+    {
+        if (Answer != _previousAnswer || Context != _previousContext)
+        {
+            _result = null;
+            _previousAnswer = Answer;
+            _previousContext = Context;
+        }
+    }
 
     protected override async Task OnParametersSetAsync()
     {
-        if (!string.IsNullOrEmpty(Answer) && !string.IsNullOrEmpty(Context) && _result == null)
+        if (_isInteractive && !string.IsNullOrEmpty(Answer) && !string.IsNullOrEmpty(Context) && _result == null)
         {
             await RunCheck();
         }
     }
 
+    protected override async Task OnAfterRenderAsync(bool firstRender)
+    {
+        if (firstRender)
+        {
+            _isInteractive = true;
+            if (!string.IsNullOrEmpty(Answer) && !string.IsNullOrEmpty(Context) && _result == null)
+            {
+                await RunCheck();
+            }
+        }
+    }
+
     private async Task RunCheck()
     {
         _isChecking = true;

src/NexusReader.UI.Shared/Pages/Home.razor

@@ -27,11 +27,10 @@
     private IJSObjectReference? _keydownHandler;
     private DotNetObjectReference<Home>? _dotNetRef;
 
-    protected override async Task OnInitializedAsync()
+    protected override void OnInitialized()
     {
         QuizState.OnQuizRequested += HandleQuizRequestedAsync;
         FocusMode.OnFocusModeChanged += HandleUpdate;
-        await FocusMode.InitializeAsync();
     }
 
     protected override async Task OnParametersSetAsync()
@@ -65,11 +64,13 @@
     {
         if (firstRender)
         {
+            await FocusMode.InitializeAsync();
             try {
                 _interopModule = await JS.InvokeAsync<IJSObjectReference>("import", "./_content/NexusReader.UI.Shared/js/focusInterop.js");
                 _dotNetRef = DotNetObjectReference.Create(this);
                 _keydownHandler = await _interopModule.InvokeAsync<IJSObjectReference>("attachKeyboardListener", _dotNetRef);
             } catch { } /* ignored dynamically */
+            StateHasChanged();
         }
     }