Check whether overdue Rillet customers are reachable in Drip

**Objective:** For every customer with overdue invoices in Rillet owing at least `{min-amount-due}` in total (default 0), show whether their email address is reachable in Drip, so collections and marketing can see who has gone quiet.

**Step 1: Find overdue invoices**

Call `rillet-get-invoices` (Rillet) once. Keep invoices marked overdue with an amount-due above zero. Group by customer-id and sum amount-due per currency. Drop customers below `{min-amount-due}`.

**Step 2: Get their emails**

Call `rillet-get-customer-emails` (Rillet) once and attach every email for each remaining customer-id, along with the customer name.

**Step 3: Check Drip**

For each email, call `drip-get-subscriber` (Drip) with email set to it. Record status, lead-score and tags. For subscribers that exist, call `drip-get-campaign-subscriber` (Drip) with the email and note any campaigns they are active in.

**Step 4: Report**

A table sorted by total amount-due, largest first: customer name, customer-id, overdue invoice count, amount-due and currency, oldest due-date, email, Drip status, active campaigns. Flag rows where every email is unsubscribed or missing in Drip as "unreachable by email".

**Rules & Guidelines:**

* The only key shared by the two systems is the email address. Rillet emails come from `rillet-get-customer-emails` (one row per address, with its customer-id and email-type); Drip emails come from the email field of `drip-get-subscriber`. Compare them trimmed and lower-cased. Never match on name alone.
* `rillet-get-customer-emails` and `rillet-get-invoices` take no filters. Call each once, keep the result, and match in memory rather than calling them per customer.
* This prompt is read-only. Do not call `drip-add-subscriber`, `drip-update-subscriber`, `drip-add-subscriber-tag`, `drip-remove-subscriber-tag`, `drip-add-subscriber-to-campaign`, `drip-remove-subscriber-from-campaign`, `drip-remove-subscriber-from-all-campaigns`, `drip-unsubscribe-subscriber`, `drip-start-subscriber-workflow`, `drip-remove-subscriber-from-workflow`, `drip-activate-campaign`, `drip-pause-campaign`, `drip-activate-workflow`, `drip-pause-workflow` on Drip, 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.
* Do not suggest pausing or unsubscribing anyone. Report only.

**Validation:**

* If no invoices are overdue, say so and stop.
* If an overdue customer has no email in Rillet, list them under "no email on file" instead of dropping them.
* Never add amounts across different currencies.