### Summary

This PR implements a timestamp feature for messages in the prompt
window, responding to feature request #944.

**What this does:**
- Prefixes each sent message with a timestamp and message version.
### Screenshot

<img width="530" height="116" alt="image"
src="https://github.com/user-attachments/assets/62a86890-b120-42dd-ab48-8eeb4515a292"
/>

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Co-authored-by: Will Chen <willchen90@gmail.com>
Co-authored-by: graphite-app[bot] <96075541+graphite-app[bot]@users.noreply.github.com>