4A: user-data drives are backup-target-eligible (not role-locked) — surfaced in
the drive purpose note. 4B: handleStorageImpact returns backup_copies (apps whose
cross-drive backups live on the drive, via backupCopiesOnPath); the wipe/eject
modal warns they'd be destroyed (stays customer-confirmable — copies redundant).
Cross-drive backup engine remains out of scope. Test: TestBackupCopiesOnPath.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
agentapi GuestAttach(where) → POST /disks/guest-attach; runStorageInit/Attach +
handleStorageRegister call attachIntoGuest after register (best-effort, P3 heals).
Closes Branch A: enrolled drives become usable in the guest, banner clears.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>