Build a Mailchimp renewal segment from Rillet contracts

**Objective:** Put the subscribed Mailchimp contacts of Rillet customers whose contracts end in the next `{days-ahead}` days (default 90) into the static segment `{segment-name}` of audience `{list-name}`, ready for a renewal campaign.

**Step 1: Resolve the audience and segment**

* Call `mailchimp-get-list` with `name.contains` set to `{list-name}`. Continue only if exactly one audience matches; keep its `list-id`.
* Call `mailchimp-get-segment` with `list-id` and `name` set to `{segment-name}`. Continue only if exactly one segment matches and its `type` is static. If it is a saved (condition-based) segment, explain that its members are set by its conditions and stop. If none matches, say so and stop; do not try to create one.
* Call `mailchimp-get-segment-member` with `segment-id` and `list-id` to get who is already in it.

**Step 2: Find the renewing customers**

Call `rillet-get-contracts` with `end-date.from` today and `end-date.to` today plus the window (YYYY-MM-DD). Exclude closed or cancelled contracts. Then call `rillet-get-customer-emails` once (no filters) to get the emails for those customers.

**Step 3: Keep only addable contacts**

Call `mailchimp-get-list-member` with `list-name` set to the confirmed audience name and `max-records` covering its size. Match emails case-insensitively after trimming spaces. A Rillet customer can have several emails (`email-type`), and one email can appear on more than one Rillet customer: keep every pairing and say so in the report. Keep emails that are members with status subscribed and are not already in the segment.

**Step 4: Show the plan and stop**

Table: email, Rillet customer name, contract name, `end-date`. Also list, separately, renewing contacts left out and why (not in audience, unsubscribed, cleaned, already in segment). Ask the user to confirm and wait.

**Step 5: Add and confirm**

For each confirmed email, call `mailchimp-add-segment-member` with `segment-id`, `list-id` and `email-address`. Then call `mailchimp-get-segment-member` with `segment-id` and report added, skipped and failed.

**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.
* The only write tool this prompt may call is `mailchimp-add-segment-member` on the mailchimp server, and only after the user confirms Step 4.
* Never call `mailchimp-add-list-member` or `mailchimp-update-list-member`: people not already subscribed stay out of the segment.
* Do not call `mailchimp-start-automation` or `mailchimp-replicate-campaign` to send anything, 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-.

**Validation:**

* If `{days-ahead}` is empty or not a whole number, use 90.
* If nothing is left to add after Step 3, report the left-out list and stop.
* If an add fails for one email, record it and continue.