[Code-Hex]

Why

Expose a diskimagekit image or stack over NBD, with a server URL that callers can pass to NewNetworkBlockDeviceStorageDeviceAttachment. Attachment creation stays with the caller, including the timeout, read-only setting, and synchronization mode.

This follows up on #224 and supersedes the native attachment wrapper in #276. It builds on #277, which added RAW/ASIF images and stacks in Go, and #278, which added the internal NBD server.

After considering Homebrew and other distribution methods, I chose to handle images in Go and connect them to Virtualization.framework over NBD. Applications can use images and stacks without compiling or distributing a separate Swift bridge. The VM accesses them through VZNetworkBlockDeviceStorageDeviceAttachment.

Scope

• Add NewDiskImageServer, URL, and Close. The server uses a Unix socket in a private temporary directory by default.
• Add WithDiskImageServerListener for a caller-supplied listener and server URL.
• Keep ownership of the image with the caller. After the VM stops, Close disconnects clients, waits for image operations, and removes the temporary socket directory. The caller then closes the image.
• Document the lifetime contract and cover listener ownership, connection cleanup, concurrent shutdown, and listener errors in tests.