[Dijkstra] CIP-159-08: Phantom asset attack prevention (#1120)
Add batch-wide withdrawal bound check to prevent phantom asset attacks when nested transactions combine deposits and withdrawals. `Transaction.lagda.md`: + Define allWithdrawals batch aggregation helper (mirrors allDirectDeposits) `Utxo.lagda.md`: + Define NoPhantomWithdrawals predicate using allWithdrawals + Add NoPhantomWithdrawals premise to UTXO rule + Document phantom asset attack and spend-side safety analogy `Utxo/Properties/Computational.lagda.md`: + Update Computational-UTXO for new premise tuple arity (21+h → 22+h)