Tag overdue Sage Intacct customers in Drip

**Objective:** Apply the Drip tag `{tag}` (default overdue-invoice) to the email contacts of Intacct customers with invoices more than `{days-overdue}` days overdue (default 30), so Drip automations can exclude or chase them. Nothing is written until the user confirms.

**Step 1: Find overdue customers in Intacct**

Call `intacct-get-invoice` with `due-date.to` set to today minus the days overdue and `total-due.min` 0.01. Group by customer-id with the overdue total. If nothing comes back, say no customer is overdue at that threshold and stop.

**Step 2: Collect their email addresses**

For each customer, call `intacct-get-customer` with `customer-id` for its email, and `intacct-get-contact` with `company-name` set to the customer-name for its contacts' emails. Drop blanks and case-insensitive duplicates.

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

Call `drip-get-subscriber` with `email` set to each one. Decide an action per email:

* Tag: the subscriber exists and its tags do not already include the tag.
* Already tagged: skip.
* Not in Drip: skip. This prompt never creates subscribers.

**Step 4: Confirm**

Show a table: customer-name, overdue total, email, Drip status, action. Give the number of emails to tag. Ask the user to confirm, and do not continue without an explicit yes.

**Step 5: Tag and verify**

For each email marked Tag, call `drip-add-subscriber-tag` with `email` and `tag`. Then call `drip-get-subscriber` for each one again and confirm the tag is present. Report tagged, already tagged, skipped and failed counts, listing every failure with its error.

**Rules & Guidelines:**

* `intacct-get-invoice`, `intacct-get-customer` and `intacct-get-contact` are on the intacct server. `drip-get-subscriber` and `drip-add-subscriber-tag` are on the drip server.
* The only write is `drip-add-subscriber-tag` on the drip server, once per email, after confirmation.
* Do not call `drip-add-subscriber` (it would create people), `drip-remove-subscriber-tag`, `drip-unsubscribe-subscriber`, `drip-start-subscriber-workflow`, `drip-update-subscriber`, `intacct-update-customer` or any other write tool on either server.

**Validation:**

* If the tag parameter is blank, use overdue-invoice.
* Unsubscribed subscribers may still be tagged, since a tag sends nothing, but mark them in the table.
* If one tag call fails, record it and carry on with the rest.
* This prompt does not remove the tag from customers who have since paid. Say that clearing it is a separate task.