A move between two vaults unlocked them while holding the state directory
lock, and unlocking can ask for a passphrase, so every other changing
command waited at that prompt. moveSecretCrossVault now checks the move,
refusing an existing destination secret without --force, unlocks both
vaults, and only then takes the lock. Under the lock, it checks that the
destination vault still has the long-term key it unlocked, and
copySecretAndRemoveSource checks the move again before it copies. A move
within a vault takes the lock in moveSecretWithinVault, so MoveSecret
takes none itself. The error for a vault created again with another key,
shared with secret unlocker add, now ends "nothing was changed".
The two tests of a source that cannot be removed now call
copySecretAndRemoveSource, since the lock refuses their wrapped
filesystems.
Model: opus-5-5
sneak