Add auto_result param to dialog items for automated validation

Each dialog test item now accepts an optional auto_result parameter
(ok/cancel/yes/no) and auto_value for text dialogs. When set, the dialog
window opens, stays visible 2 seconds, then closes automatically with the
specified result — allowing the validation suite to run without manual
interaction.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

test/validation/items/plot/test.tum

@@ -71,4 +71,4 @@
     steps:
         - close:
             wait_dialog_exit: True
-            timeout: 60
+            timeout: 2