Fix the lifetime revenue report per customer

An AI's SQL report joined both orders and refunds to customers in one query. A customer with 10 orders and 4 refunds became 40 rows, so revenue came out 4 times too high. The new version totals each table on its own and only then attaches the results to the customer.

An assistant wrote customer_revenue_report(customer_ids, order_rows, refund_rows). It is in the editor. It has a bug. Find it and fix it.

Input and output:

• customer_ids: the customers to report on. An id can be listed more than once.
• order_rows: one order per row, written customer_id,amount, with the amount in cents.
• refund_rows: one refund per row, written customer_id,refund_id. The same refund can appear in more than one row.
• Return one customer_id:revenue:refund_count string per customer.

Rules the tests check:

• Report each distinct customer id once, sorted as plain strings. A customer with no orders or refunds still appears, with 0 for both.
• Split each order row on ,. Skip it unless it has exactly 2 parts, its customer is in customer_ids, and its amount is an optional - followed by one or more digits from 0 to 9. A customer's revenue is the sum of their amounts.
• Split each refund row on ,. Skip it unless it has exactly 2 parts and its customer is in customer_ids. A customer's refund count is the number of different refund ids they have: the same refund id listed twice counts once.