feat: add timestamp to Message types (#258)

[danielsiwiec]

No description provided.

[ashwin-ant]

Can you clarify why this is needed? This doesn't seem like it needs explicit SDK support.

[danielsiwiec]

@ashwin-ant the parse_message function provides convenient access to claude's internal data model stored in the JSONL files, by parsing them into the Message types (UserMessage, AssistantMessage, etc). I think it's helpful for these types to expose all fields stored in the JSONL messages, like the timestamp or the parent_tool_use_id merged recently.

Two use cases that come to mind:

• asynchronous, event-driven consumption of the Message types - if the application consumes the Messages from a queue, the time of consumption can be quite different from the time of the message 'production'
• restoring agent state at a later time, from JSONL files, using parse_message - if messages are restored at a later point, not having the timestamp exposed makes it impossibe to determine it's timing (without manually reading the JSONL file)

Does this make sense?

I put some short version of this context on the issue, as well