[kvinwang]

A first boot interrupted between luksFormat and mkfs leaves a LUKS header with no filesystem behind it. Every later boot fails to mount the data disk and the CVM reboots forever.

Change

• luksFormat sets the LUKS2 label dstack-initializing; it is cleared (cryptsetup config --label=) once the filesystem exists.
• On boot, an encrypted disk whose header still carries the label is initialized again. Any other disk is mounted as before, so a damaged but recoverable filesystem is never reformatted.
• The header validator accepts exactly this label (any other non-empty label is still rejected) and reports it from the in-memory header it already validated, so there is no second read of the disk.
• On that retry only, zpool labelclear -f drops a pool label left by an interruption after zpool create, which would otherwise block zpool create (ext4 already uses mkfs.ext4 -F). First-time initialization is unchanged.

Disks initialized by earlier builds have an empty label and are unaffected. The label is in the unauthenticated header, so a host can force a re-initialization, but it could already do so by erasing the header.

Verification

• cargo test -p dstack-util (112 passed), fmt, clippy clean.
• Headers produced by cryptsetup luksFormat --label dstack-initializing and after cryptsetup config --label= validate as Ok(true) / Ok(false).
• On a loop device mapped through a detached header, mkfs.ext4 then cryptsetup config --label= succeeds, the label is gone, and the ext4 behind it is intact.