test: stabilize text-area visual tests by disabling input-field transition (#11588)

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: web-padawan

packages/text-area/test/visual/common.js

@@ -10,6 +10,7 @@ registerStyles(
 
     /* Show error message immediately */
     [part='label'],
+    [part='input-field'],
     [part='helper-text'],
     [part='error-message'],
     [part='required-indicator'] {