fix(amazonq): include more context on chat response error (#5900)

Sometimes the error body is not actually useful
```
An unexpected error occurred, check the logs for more information.
```

After:
```
McpManager not initialized—call McpManager.init(...) first: An unexpected error occurred, check the logs for more information.
```

Author: rli

plugins/amazonq/shared/jetbrains-community/src/software/aws/toolkits/jetbrains/services/amazonq/lsp/flareChat/ChatCommunicationManager.kt

@@ -200,7 +200,7 @@ class ChatCommunicationManager(private val project: Project, private val cs: Cor
         var errorMessage: String? = null
         if (exception is ResponseErrorException) {
             errorMessage = tryOrNull {
-                Gson().fromJson(exception.responseError.data as JsonObject, ChatMessage::class.java).body
+                "${exception.responseError.message}: ${Gson().fromJson(exception.responseError.data as JsonObject, ChatMessage::class.java).body}"
             } ?: exception.responseError.message
         }