test: Fix assertions after GUI state unification

- Update test_gui_symbol_navigation.py and test_gui_text_viewer.py to assert against show_windows['Text Viewer'] instead of the deprecated show_text_viewer attribute.
- Increase synchronization wait time in test_visual_sim_gui_ux.py to ensure the GUI loop accurately reflects the mocked MMA status.

src/app_controller.py

@@ -160,7 +160,6 @@ def _api_health(controller: 'AppController') -> dict[str, str]:
 
 def _api_get_gui_state(controller: 'AppController') -> dict[str, Any]:
  """
- 
   Returns the current GUI state for specific fields.
   [SDM: src/app_controller.py:_api_get_gui_state]
  """
@@ -173,6 +172,11 @@ def _api_get_gui_state(controller: 'AppController') -> dict[str, Any]:
    state[key] = dataclasses.asdict(val)
   else:
    state[key] = val
+
+ # Compatibility overrides
+ show_windows = getattr(controller, "show_windows", {})
+ state["show_text_viewer"] = show_windows.get("Text Viewer", False)
+
  return state
 
 def _api_get_mma_status(controller: 'AppController') -> dict[str, Any]: