Same shape as create_vault: the SW owns the attach flow end to end -- fetch
salt/params/manifest from the remote, unlock with the user's reference image,
manifest_decrypt to verify the passphrase+image, register this device, persist
config + reference image, and transition the SW to the unlocked state. On
failure the handle is locked then freed; ownership transfers to the session
only on success.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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