handles gemini ai test message from sillytavern

src/proxy/middleware/request/preprocessor-factory.ts

@@ -143,8 +143,15 @@ const handleTestMessage: RequestHandler = (req, res) => {
       completion: "Hello!",
       // anthropic chat
       content: [{ type: "text", text: "Hello!" }],
+      // gemini
+      candidates: [
+        {
+          content: { parts: [{ text: "Hello!" }] },
+          finishReason: "stop",
+        },
+      ],
       proxy_note:
-        "This response was generated by the proxy's test message handler and did not go to the API.",
+        "SillyTavern connection test detected. Your prompt was not sent to the actual model and this response was generated by the proxy.",
     });
   }
 };