Focus inventory sign-off on the gaps worth real money

**Objective:** Confirm that Dynamics GP inventory items were migrated to Business Central with matching setup and quantity on hand, for item `{item-number}` or, if that is empty, every GP item that is not discontinued.

**Step 1: Read the GP items**

Call `dynamics-gp-get-iv-item`, with `item-number` set to `{item-number}` when it is given, and a `max-records` large enough for the item list. Leave out items whose item-type is Discontinued; they are commonly left behind on purpose, so count them but do not report them as missing.

**Step 2: Read the GP quantities**

Call `dynamics-gp-get-iv-item-quantity` with the same `item-number` filter. Use the item-total row for each item (the one whose record-type is the overall item record, not a site). If only site rows come back, add up quantity-on-hand per item-number across sites.

**Step 3: Read the BC items**

Call `business-central-get-item`, with `item-number` set to `{item-number}` when it is given. Match GP `item-number` to BC `item-number`, trimmed and case-insensitive.

**Step 4: Compare each matched pair**

* item-description vs description
* base-u-of-m vs base-unit-of-measure
* current-cost vs unit-cost, and standard-cost vs standard-cost (flag a difference over 1 percent)
* quantity-on-hand vs inventory
* item-type vs type: GP Sales Inventory maps to BC Inventory, GP Services and Flat Fee map to BC Service, GP Misc Charges maps to BC Non-Inventory

**Step 5: Report**

Counts first: matched clean, matched with differences, missing from BC, discontinued and skipped. Then a table of quantity differences (item, GP on hand, BC inventory, difference), sorted by the absolute difference times current-cost so the largest value gaps come first. Then a table of the other differences.

**Rules & Guidelines:**

* `dynamics-gp-get-iv-item` and `dynamics-gp-get-iv-item-quantity` are on the dynamics-gp server. `business-central-get-item` is on the business-central server.
* This prompt is read-only. Do NOT call `business-central-create-item`, `business-central-update-item`, `dynamics-gp-iv-item-add` or `dynamics-gp-iv-item-update`.
* 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 BC has the item but inventory is 0 for every item, report that opening quantities have not been posted in BC yet, instead of listing every item as a quantity difference.
* If GP and BC were not read at the same moment, quantities can drift on a live system. Say so when the GP company is still posting transactions.