Find BigCommerce pricing errors before they cost margin

**Objective:** Audit product pricing for problems, limited to brand `{brand-name}` or to products priced at or above `{min-price}` if given.

**Step 1: Pull products**

Call `bigcommerce-get-product` (with `brand-id` after resolving `{brand-name}` via `bigcommerce-get-brand`, and `price.min` if given). Read `price`, `sale-price`, `retail-price`, `cost-price` and `calculated-price`.

**Step 2: Check each product**

Flag when:

* `price` is zero or empty.
* `sale-price` is above `price`.
* `cost-price` is above the selling price (negative margin).
* `retail-price` is below `price`.
* Margin ((price - cost-price) / price) is under 10 percent while `cost-price` is set.

**Step 3: Check variants for flagged products**

For up to 20 flagged products, call `bigcommerce-get-product-variant` with `product-id` and look for variants whose own `price` or `sale-price` causes the same issue.

**Step 4: Report**

Table: product id, name, sku, issue, the figures. Sort by severity (negative margin, then zero price, then the rest). End with a count per issue type.

**Rules & Guidelines:**

* This is a read-only job. Never call any `bigcommerce-*-add`, `bigcommerce-*-update` or `bigcommerce-*-delete` tool. Do not suggest that you changed anything.
* Recommend corrections only; do not change any price.

**Validation:**

* If a read returns no records, say so plainly and stop; do not invent figures.
* If a result hits the maximum records limit, say the figures may be incomplete and name the filter that would narrow it.