Summarize the transactions in ledger.json. Only status "posted" counts. For each account, net_cents is sum of credit amounts minus sum of debit amounts, and count is the number of posted transactions. Produce summary.json containing exactly {"batch": <ledger batch>, "accounts": <account-name-sorted list of {"account": name, "net_cents": integer, "count": integer}>}. Do not include accounts with zero posted transactions. All amounts are integer cents. Check by running python3 verify.py.
