#3585452 Create preview for translations

Testing steps

• Install Drupal with the minimal profile
• Enable the canvas, canvas_test_sdc, and canvas_test_recipe modules: drush en canvas canvas_test_sdc canvas_test_recipe
• Apply the test translation recipe: php core/scripts/drupal recipe modules/contrib/canvas/tests/fixtures/recipes/test_translation -vvv
• Navigate to canvas/editor/canvas_page/1
• Verify the Language Selector dropdown is visible on the right side of the top bar (showing "English")
• Select French: The page should load in preview mode showing French content ("Bonjour, Canvas!" and "Bonjour de la région")
• Select Spanish: The page should fall back to English content (no Spanish translation exists)
• Select Default (English): The view should return to the editor with no ?language= query parameter in the URL