Tell late payers from silent ones with Constant Contact data

**Objective:** For every Rillet customer with an overdue invoice whose amount due is at least `{min-amount-due}` (default 0), show whether their billing contacts are still opening and clicking Constant Contact email in the last `{lookback-days}` days (default 30), so collections can tell an unresponsive customer from one who is simply late.

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

Call `rillet-get-invoices` (rillet server). It takes no filters, so keep rows where `overdue` is true and `amount-due` is at least the minimum. Group by `customer-id` and, per customer, record the number of overdue invoices, the oldest `due-date`, and the total `amount-due` by `currency`.

If no invoice is overdue, report that and stop.

**Step 2: Resolve each customer's emails**

Call `rillet-get-customer-emails` (rillet server) once and keep the rows whose `customer-id` is in Step 1. A customer may have several emails; keep them all. A customer with no email is reported as "no email on file in Rillet" and skipped for Step 3.

**Step 3: Read engagement in Constant Contact**

For each email, call `constant-contact-get-contact` (constant-contact server) with `email-address`. If no contact comes back, record "not in Constant Contact". Otherwise, with `contact-id` and `created-date.from` set to today minus the lookback, call `constant-contact-get-campaign-open`, `constant-contact-get-campaign-click` and `constant-contact-get-campaign-bounce` (constant-contact server). Record the counts and the most recent open or click date.

**Step 4: Report**

A table sorted by oldest due date:

| Customer | Overdue invoices | Oldest due date | Amount due (by currency) | Emails | Opens | Clicks | Last opened or clicked | Bounced |

Then classify each customer as one of: **Engaged but unpaid** (opens or clicks in the window), **Silent** (in Constant Contact, no opens or clicks), **Unreachable** (bounced, or not in Constant Contact, or no email on file). Recommend a phone call for Silent and Unreachable customers.

**Rules & Guidelines:**

* Tools starting rillet- are on the rillet server; tools starting constant-contact- are on the constant-contact server.
* Match emails exactly, ignoring case and surrounding spaces. Never match on company name.
* Never add amounts in different currencies.
* This prompt is read-only. Do not call `rillet-add-invoice-payment`, `rillet-set-invoice-sent-status` or any other rillet-add-* or rillet-update-* tool, and do not call `constant-contact-add-contact-note`, `constant-contact-add-campaign` or any other constant-contact-add-* or constant-contact-update-* tool.

**Validation:**

* If a customer has several emails, sum their engagement and list the emails.
* If `{min-amount-due}` is not a number, treat it as 0 and say so.