execute method
Evaluates this condition configuration.
The context
parameter provides access to the widget tree.
Returns:
- null if the condition passes
- an error message string if the condition fails
Implementation
@override
Future<String?> execute(BuildContext context) async {
// Return error message that causes condition to fail
// The visual feedback is already shown during deserialization
return 'Missing condition: $missingSchemaType';
}