`ciel farewell` panics when a file is already missing

[lhz07]

✔ Name of the instance · main
info: Understood. `main` will be created after initialization is finished.
info: Initializing workspace...
info: Initializing container OS...
info: Searching for latest AOSC OS buildkit release...
info: Ciel has picked buildkit for arm64, released on 20260621
info: Downloading base OS rootfs...
info: Verifying tarball checksum...
info: Checksum verified.
info: Initializing ABBS tree...
[████░░░░░░░░░░░░░░░░░░░░░] 165156/924070 45.51 MiB (145248297y)                                                   ^Croot@aosc [ ~ ] ! ls
TREE  aosc-os_buildkit_20260621_arm64.squashfs

The progress seems to be stuck while initializing the ABBS tree, so I pressed Ctrl+C to stop the process.
After that, Ciel says that I need to clean up the workspace first:

root@aosc [ ~ ] # ciel new
info: Welcome to ciel!
error: Seems like you've already created a ciel workspace here.
info: Please run `ciel farewell` to nuke it before running this command.
error: Unable to create a ciel workspace.

I then ran ciel farewell:

root@aosc [ ~ ] ! ciel farewell
✔ DELETE THIS CIEL WORKSPACE? · yes
info: If you are absolutely sure, please type the following:
Do as I say!
✔ Your turn · Do as I say!
info: ... as you wish. Commencing destruction ...
info: Un-mounting all the instances...
>>> update-662d42f2

thread 'main' (700) panicked at src/main.rs:151:43:
called `Result::unwrap()` on an `Err` value: I/O error: No such file or directory (os error 2)

Caused by:
    No such file or directory (os error 2)
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

When removing files during workspace cleanup, it would be better to ignore io::ErrorKind::NotFound errors (or log them if necessary) rather than propagating the error and finally panicking.