[Feature Request] Add timestamp to /export filename to prevent overwrites

Question

**Feedback Description**
it would be great if the `/export` filename output format can be like `2025-12-31 11:22:33 some_message.txt` the important part is the time, because i oftenly use this to store the conversation. but due to the same name it will replace the old one. and this is very annoying. i need to rename it manually again and again. And of course we can also skip the read/write file and only store the thinking and ai answer part.

**Environment Info**
- Platform: darwin
- Terminal: v