Replace the error message the AI Client returns with a more specific one if image requests fail

includes/Abilities/Image/Generate_Image.php

@@ -256,6 +256,17 @@ private function get_prompt_builder( string $prompt, ?string $reference_image =
 			}
 		}
 
+		// Return a more specific error if there isn't a model that supports image generation.
+		if ( ! $prompt_builder->is_supported_for_image_generation() ) {
+			$error_message = esc_html__( 'Image generation failed. Please ensure you have a connected provider that supports image generation.', 'ai' );
+
+			if ( null !== $reference_image ) {
+				$error_message = esc_html__( 'Image refinement failed. Please ensure you have a connected provider that supports image refinement, not just image generation.', 'ai' );
+			}
+
+			return new WP_Error( 'unsupported_model', $error_message );
+		}
+
 		return $prompt_builder;
 	}
 }