docs: add XML documentation and ConfigManager implementation plans

Add comprehensive XML documentation (param/returns tags) across 132 source
files to improve IntelliSense and API discoverability. Include ConfigManager
design documents and implementation plans for phases 1-9.

NEW/src/Utils/JdeScoping.SecureStoreManager/ViewModels/RelayCommand.cs

@@ -11,6 +11,9 @@ public class RelayCommand : ICommand
     private readonly Predicate<object?>? _canExecute;
     private EventHandler? _canExecuteChanged;
 
+    /// <summary>
+    /// Raised when the command's ability to execute may have changed.
+    /// </summary>
     public event EventHandler? CanExecuteChanged
     {
         add => _canExecuteChanged += value;
@@ -56,11 +59,20 @@ public class RelayCommand : ICommand
     {
     }
 
+    /// <summary>
+    /// Determines whether the command can execute.
+    /// </summary>
+    /// <param name="parameter">An optional command parameter.</param>
+    /// <returns>True if the command can execute, false otherwise.</returns>
     public bool CanExecute(object? parameter)
     {
         return _canExecute == null || _canExecute(parameter);
     }
 
+    /// <summary>
+    /// Executes the command with the specified parameter.
+    /// </summary>
+    /// <param name="parameter">An optional command parameter.</param>
     public void Execute(object? parameter)
     {
         _execute(parameter);