Encodes DelegationManager.delegateTo(operator, ...). Delegates all staker shares to one operator.
Note: delegation is all-or-nothing. Switching operators requires undelegating first (14-day escrow).

The operator is automatically set to the Stakefish operator — no operator parameter is accepted.

Nonce handling: The nonce is computed at call time. If you prepare multiple transactions before broadcasting, they will share the same nonce and only the first will succeed. Broadcast and confirm each transaction before preparing the next.