Zed should preserve file undo history when it's closed and opened again

[polina4096]

Check for existing issues

• Completed

Describe the feature

In all other IDEs, if you:

1. open a file, make an edit
2. save the file and close it
3. reopen the file

it's possible to undo the edit which was made.

Unfortunately, that does not match current Zed behavior, which loses all history upon file reopen. I propose that Zed should match the expected behavior and preserve undo history for all files for at least the current session, which means it should not lose the undo history when the file is closed.

Should be quite a simple fix, at least to preserve the history only for the current session.

Zed Version and System Specs

Zed: v0.168.3 (Zed)
OS: macOS 15.3.0
Memory: 36 GiB
Architecture: aarch64

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

No response