Tag buyers of a WooCommerce product in Drip for follow-up

**Objective:** Tag in Drip everyone who bought the WooCommerce product with SKU `{product-sku}` in the last `{lookback-days}` days (default 90), using the tag `{tag}`.

**Step 1: Confirm the product**

Call `woocommerce-get-product` with `sku` set to `{product-sku}`. If nothing comes back, call `woocommerce-get-product-variation` with the same `sku`. If neither finds it, or more than one product matches, list what you found and stop. Note the product name.

**Step 2: Find the buyers**

Call `woocommerce-get-order-line` with `line-sku` set to `{product-sku}`, `date-created.from` set to today minus `{lookback-days}` days, and `max-records` set to 500. Drop lines whose order status is cancelled, failed or refunded. Collect the distinct customer emails, with each buyer's quantity and last purchase date.

**Step 3: Check each buyer in Drip**

For each email, call `drip-get-subscriber` with `email` set to it. Sort buyers into: subscribed in Drip, already carrying `{tag}`, unsubscribed in Drip, and not in Drip.

**Step 4: Confirm**

Show the counts per group and the list of subscribed buyers who will be tagged. Ask the user to confirm. Do not continue without a clear yes.

**Step 5: Tag and verify**

For each confirmed subscribed buyer who does not already have the tag, call `drip-add-subscriber-tag` once with `email` and `tag` set to `{tag}`. Then re-read a sample of up to 5 with `drip-get-subscriber` and confirm the tag shows. Report tagged, failed, and skipped by reason.

**Rules & Guidelines:**

* Tools whose names start with drip- are on the drip server; tools whose names start with woocommerce- are on the woocommerce server. Both servers must be connected.
* Match people across the two systems by email, compared case-insensitively with surrounding spaces removed. Drip uses `email`; WooCommerce uses `email` on customers and `customer-email` on orders, order lines and refunds.
* Compute dates as today minus the stated number of days and pass them as YYYY-MM-DD.
* The only write allowed is `drip-add-subscriber-tag`, for subscribed buyers only, after the user confirms in Step 4.
* Never tag buyers who are not in Drip or who are unsubscribed: tagging an unknown email creates a new Drip subscriber. List them instead.
* Do not call `drip-add-subscriber`, `drip-update-subscriber` or `drip-add-subscriber-to-campaign`.
* Make no changes in WooCommerce. Do not call `woocommerce-add-customer`, `woocommerce-update-customer`, `woocommerce-update-order`, `woocommerce-add-order-note`, `woocommerce-add-coupon` or `woocommerce-add-refund`.

**Validation:**

* If no qualifying order lines come back, say so and stop.
* Order lines with a blank customer email are guest orders with no address to match; count them and leave them out.
* If an order line's SKU differs only in case from `{product-sku}`, treat it as the same product.