[Feature]: `ToolCallArgsEvent` should have a `parentMessageId` field.

### Pre-flight Checklist

- [x] I have searched existing issues and this hasn't been requested yet.

### Problem or Motivation

The "started" and "chunk" events have this field, the "args" event should have it as well.

When applying events directly as patches to messages, the lack of `parentMessageId` requires a double search through each message, then all the tools for each message.

### Proposed Solution

Add a `parentMessageId` field to the `ToolCallArgsEvent`.

### Alternatives Considered

_No response_

### Additional Context

_No response_