Partially downloaded/damaged Xcode archives aren't checked before moved to download location

[i0ntempest]

To reproduce:

1. Run xcodes download --latest-prerelease
2. Make it fail for some reason. I get:

 Received 403: Unauthorized. This can happen when either:
 1. Apple Developer Terms and Conditions were not accepted at https://developer.apple.com/
 2. Apple ID authorization was revoked for some other reason

Even after I log in.
3. Run the downloaded command again
4. Get:

Updating...
Latest prerelease version available is 27.0 Beta 2

(1/1) Found existing archive at /Users/Admin/Library/Application Support/com.robotsandpencils.xcodes/Xcode-27.0.0-Beta.2+27A5209h.xip.

Xcode 27.0.0-Beta.2 has been downloaded to /Users/Admin/Downloads/Xcode-27.0.0-Beta.2+27A5209h.xip

Which is an invalid archive from the previous failed download.