No transaction persistence - pending txs lost on restart

Problem

There's no built-in way to track pending transactions across application restarts. If the application crashes or restarts while transactions are pending, that state is lost.

Impact

• Users can't recover pending transaction status after restart
• waitForTransaction doesn't work across sessions
• Difficult to build reliable payment flows

Recommendation

1. Add optional transaction state persistence layer
2. Allow users to provide storage adapter (localStorage, file, database)
3. Track: txHash, nonce, timestamp, status

interface TransactionStore {
  save(tx: PendingTransaction): Promise<void>;
  load(txHash: Hash): Promise<PendingTransaction | null>;
  listPending(): Promise<PendingTransaction[]>;
  markConfirmed(txHash: Hash, receipt: TransactionReceipt): Promise<void>;
}

// Usage
const wallet = new AgentWallet({
  // ...
  transactionStore: new FileTransactionStore('./tx-state.json'),
});

Priority

High - Reliability for production use

Start by tracing AgentWallet's transaction handling and the waitForTransaction flow. Use the proposed TransactionStore interface and listed fields as the scope, then verify that pending transactions can be recovered after a restart and that confirmation updates persisted state.