dismissed assistant panel during collab has no title

[notpeter]

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Describe the bug / provide steps to reproduce it

Steps to reproduce:

1. Open a collab session
2. Remote user uses assistant panel
3. Remote user closes the assistant panel
4. User following gets no title assistant panel.

I imagine this Assistant buffer should be dismissed locally as well.

Environment

Zed: v0.159.0 (Zed Nightly dc4396b)
OS: macOS 14.7.0
Memory: 64 GiB
Architecture: aarch64

If applicable, add mockups / screenshots to help explain present your vision of the feature

If applicable, attach your Zed.log file to this issue.

No response