* `has_conflict` will now return true if the file has been deleted on
disk. This is for treating multi-buffers as conflicted, and also
blocks auto-save.
* `has_deleted_file` is added so that the single-file buffer save can
specifically mention the delete conflict. This does not yet handle
discard (#20745).
Closes#9101Closes#9568Closes#20462
Release Notes:
- Improved handling of externally deleted files: auto-save will be
disabled, multibuffers will treat this as a save conflict, and single
buffers will ask for restore confirmation.
Co-authored-by: Conrad <conrad@zed.dev>