Fix: Implement SuggestedActionsChanged as no-op event property

The ISuggestedActionsSource interface requires the SuggestedActionsChanged event.
This implementation uses a pull model (VS calls HasSuggestedActionsAsync/GetSuggestedActions
on-demand) rather than push model (raising events). Implemented as a no-op property
to satisfy the interface contract while suppressing code analysis warnings.

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

Author: cx-rahul-pidde

ast-visual-studio-extension/CxExtension/CxAssist/Core/Markers/CxAssistSuggestedActionsSource.cs

@@ -25,6 +25,12 @@ public CxAssistSuggestedActionsSource(ITextView textView, ITextBuffer textBuffer
             _textBuffer = textBuffer ?? throw new ArgumentNullException(nameof(textBuffer));
         }
 
+        public event EventHandler<EventArgs> SuggestedActionsChanged
+        {
+            add { }
+            remove { }
+        }
+
         public void Dispose()
         {
         }