Prove customer balances carried over, document by document

**Objective:** Prove that open receivables carried over from Dynamics GP to Business Central, for customer `{customer-id}` or, if that is empty, every GP customer with a balance. Compare balances as of `{cutover-date}` (if that is empty, compare current balances and say so).

**Step 1: Read the GP balances**

Call `dynamics-gp-get-rm-customer` with `customer-id` set to `{customer-id}` when it is given. Keep customers whose customer-balance is not zero.

**Step 2: Read the BC balances**

Call `business-central-get-customer` for the same customers and match GP `customer-id` to BC `customer-number`, trimmed and case-insensitive. When `{cutover-date}` is empty, use BC balance. When it is given, BC balance also includes activity after go-live, so for any customer whose balance differs, call `business-central-get-detailed-customer-ledger` with `customer-number` and `posting-date.to` set to `{cutover-date}`, and use the sum of amount instead.

**Step 3: Find the documents behind each difference**

For each customer whose GP and BC balances differ by more than 0.01:

1. Call `dynamics-gp-get-rm-trx` with `customer-id`, leaving out voided documents. Keep documents whose current-transaction-amount is not zero.
2. Call `business-central-get-detailed-customer-ledger` with `customer-number`. Group its rows by customer-ledger-entry-number and add up amount to get each entry's remaining amount.
3. Match GP document-number to BC document-number. The GP migration usually keeps the GP document number on the opening entry.

GP stores payments, credit memos and returns as positive amounts; BC stores them as negative. Flip the sign of those GP document types before comparing.

**Step 4: Report**

A summary line: customers compared, customers in balance, customers out of balance, total GP open AR, total BC open AR, net difference. Then, per out-of-balance customer: GP balance, BC balance, difference, and the documents that explain it (open in GP but missing from BC, in BC but not open in GP, or open in both with different remaining amounts).

**Rules & Guidelines:**

* `dynamics-gp-get-rm-customer` and `dynamics-gp-get-rm-trx` are on the dynamics-gp server. `business-central-get-customer` and `business-central-get-detailed-customer-ledger` are on the business-central server.
* This prompt is read-only. Do NOT call `business-central-create-journal-line`, `business-central-create-sales-invoice`, `business-central-create-sales-credit-memo` or `dynamics-gp-rm-trx-add`.
* If either system has more than one company, ask the user which GP company and which BC company to use before the first call, and pass them as `company`.

**Validation:**

* If a GP customer with a balance has no BC customer, report it as a missing customer with its full balance and do not look for documents.
* If the balances differ but no single document explains it, report the unexplained remainder rather than guessing.
* Some migrations bring AR over as one summary entry per customer. If BC has one entry per customer whose amount equals the GP balance, report the customer as in balance at summary level.