Rate upcoming Rillet renewals by Mailchimp engagement

**Objective:** For Rillet contracts ending in the next `{days-ahead}` days (default 90), check whether the customers' contacts are still reachable and engaged in Mailchimp, and flag the renewals at risk.

**Step 1: Find the renewals**

Call `rillet-get-contracts` with `end-date.from` set to today and `end-date.to` set to today plus the window (YYYY-MM-DD). Exclude contracts whose `status` shows they are already closed or cancelled. If none remain, say there are no renewals in the window and stop.

**Step 2: Find each customer's contacts**

Call `rillet-get-customer-emails` once (no filters) and keep the emails for each `customer-id` from Step 1. A customer with no emails is reported as "no contact email in Rillet".

**Step 3: Check Mailchimp for each email**

* Call `mailchimp-get-list-member` with `email`. Record each audience's `status`, `average-open-rate` and `last-changed-date`.
* Call `mailchimp-get-campaign-email-activity` with `email-address` and `activity-date.from` set to 90 days ago. Record the last open or click date and any bounces.

**Step 4: Classify and report**

Classify each contract by the best-engaged contact on its customer:

* **Engaged:** at least one subscribed contact opened or clicked in the last 90 days.
* **Silent:** subscribed, but no opens or clicks in 90 days.
* **Unreachable:** every contact is unsubscribed, cleaned, bouncing, or not in Mailchimp at all.

Report a table sorted by `end-date`: customer name, contract name, `end-date`, `total-value` and `currency`, classification, best contact email, last engagement date. Then summarise the count and total value per classification.

**Rules & Guidelines:**

* Tools named mailchimp- come from the mailchimp MCP server; tools named rillet- come from the rillet MCP server. If a tool from either server is missing, stop and say which server is not connected rather than working around it.
* The only key shared by the two systems is the email address. Mailchimp `customer-id` values (e-commerce store customers) are NOT Rillet customer ids; never pass one system's id into the other.
* Read-only. Do not call any Mailchimp tool whose name starts with mailchimp-add-, mailchimp-update-, mailchimp-start-, mailchimp-pause- or mailchimp-replicate-, and do not call any Rillet tool whose name starts with rillet-add-, rillet-update-, rillet-apply-, rillet-unapply-, rillet-record-, rillet-set- or rillet-setup-. In particular never call `mailchimp-add-list-member`, `mailchimp-update-list-member` or `mailchimp-add-segment-member` from this prompt.

**Validation:**

* If `{days-ahead}` is empty or not a whole number, use 90.
* Do not add `total-value` across currencies.
* If a Mailchimp lookup fails for one email, mark that contact as "unknown" and continue.