LanguageModelFailurePlugin and LanguageModelRateLimitingPlugin incorrectly displays warning when `languageModel.enabled` property not present

<img width="1021" height="466" alt="Image" src="https://github.com/user-attachments/assets/6fa9af5d-9a9e-4b4c-8485-70dac16a1b01" />

Let's check the other LanguageModel plugins whilst we work on this.