This PR adds support for deleting your entire thread history. This is
inspired by a Zed user from the meetup in Amsterdam, he was missing this
feature.

**Demo**


https://github.com/user-attachments/assets/5a195007-1094-4ec6-902a-1b83db5ec508

Release Notes:

- AI: Add support for deleting your entire thread history

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Co-authored-by: Danilo Leal <daniloleal09@gmail.com>