chat.params can't modify system?

Are you sure the injection system works? As far as I understand this hook can't modifiy the system prompt, just the provider params.

```typescript
"chat.params"?: (
    input: { sessionID: string; agent: string; model: Model; provider: ProviderContext; message: UserMessage },
    output: { temperature: number; topP: number; options: Record<string, any> },
  ) => Promise<void>
```
