Breaking: Gemini 3.1 Flash Image Preview and 3 Pro Image Preview are retired

Gemini 3.1 Flash Image Preview and 3 Pro Image Preview are retired

The Nano Banana preview models gemini-3.1-flash-image-preview and gemini-3-pro-image-preview have been retired and are no longer accessible. Update your code to use either gemini-3.1-flash-image or gemini-3-flash-image instead.