Improper types for `ctx.sample`

### Description

the messages is `list[str | SamplingMessage]`, it should be a Sequence so users dont get type errors if they pass a `list[str]` or a `list[SamplingMessage]` and the return type can only be text, audio, image, not all the types in ContentBlock

### Example Code

```Python

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### Version Information

```Text
latest
```