Remove non-existent UndoableCommand methods from documentation

Removed fictional methods that don't exist in actual API:
- redo() - does not exist
- canUndo - does not exist
- canRedo - does not exist
- clearStack() - does not exist

Only undo() method exists in UndoableCommand class.

Verified against: undoable_command.dart (complete file read, only undo() at line 86)

Author: escamoteur

docs/documentation/command_it/command_types.md

@@ -179,13 +179,7 @@ All other parameters (`initialValue`, `restriction`, `errorFilter`, etc.) work t
 
 **Additional methods:**
 
-Undoable commands provide undo/redo functionality:
-
-- **`undo()`** - Undo the last operation
-- **`redo()`** - Redo the last undone operation
-- **`canUndo`** - `ValueListenable<bool>` indicating if undo is available
-- **`canRedo`** - `ValueListenable<bool>` indicating if redo is available
-- **`clearStack()`** - Clear the entire undo/redo stack
+- **`undo()`** - Manually undo the last operation by calling the undo handler. The undo handler receives the `UndoStack` and can pop state to restore previous values
 
 **See also:**
 - [Best Practices - Undoable Commands](/documentation/command_it/best_practices#pattern-5-undoable-commands-with-automatic-rollback) for practical examples