See which Rillet contracts renew soon and what is at stake

**Objective:** List every customer contract ending in the next `{days-ahead}` days (default 90), optionally only for `{customer-name}`, ranked by the recurring revenue at stake.

**Step 1: Resolve the customer (only if one was given)**

If `{customer-name}` is not empty, call `rillet-get-customers` and find the matching customer. If more than one matches, list them and stop.

**Step 2: Pull the contracts**

Call `rillet-get-contracts` with `end-date.from` = today and `end-date.to` = today plus `{days-ahead}` days (and `customer-id` if resolved). Then call `rillet-get-contract-items` filtered by each `contract-id`.

**Step 3: Size what is at stake**

* Call `rillet-get-arr-waterfall` filtered by each `customer-id` and take the latest `year-month`.
* Call `rillet-get-invoices` (no filters) and note any open `amount-due` for the customer; a renewal conversation with an unpaid balance needs to know that.

**Step 4: Report**

Sorted by current ARR, highest first: customer, contract name, end date, days left, total value, current ARR, items (product and quantity), open balance, and a short note (for example usage commitment, or ARR falling).

**Rules & Guidelines:**

* This is read-only. Do not call any tool whose name starts with rillet-add-, rillet-update-, rillet-apply-, rillet-unapply-, rillet-record-, rillet-set- or rillet-setup-. In particular do not call `rillet-record-contract-usage`.
* Leave out contracts whose `status` shows they are already cancelled or ended, and say how many.
* Never add amounts in different currencies together.

**Validation:**

* If nothing ends in the window, say so and give the next contract end date you can see.