fix(ai): Only include unexpected prediction element in error message (#9222)

* fix(ai): Only include unexpected prediction element in error message.

If the `responseJson` from the Predict request has an image, the entire
image base64 will be included in the error message. This can make the error
message >400kB (!!), which could cause performance issues in apps.

I ran into this when testing #9216,
since the `safetyAttributes` would be included in a response and trigger
this error, but the `predictions` array in `responseJson` would have images.
I noticed that when the sample app rendered the `error.message`, it
began running into serious performance issues.

Author: dlarocque

.changeset/calm-guests-pump.md

@@ -0,0 +1,5 @@
+---
+'@firebase/ai': patch
+---
+
+Fixed an issue where `AIError` messages were too long after including an entire response body.

packages/ai/src/requests/response-helpers.ts

@@ -298,9 +298,9 @@ export async function handlePredictResponse<
     } else {
       throw new AIError(
         AIErrorCode.RESPONSE_ERROR,
-        `Predictions array in response has missing properties. Response: ${JSON.stringify(
-          responseJson
-        )}`
+        `Unexpected element in 'predictions' array in response: '${JSON.stringify(
+          prediction
+        )}'`
       );
     }
   }