Put Stripe churn signals on the Salesforce renewal

**Objective:** For the open Salesforce opportunity `{opportunity-name}`, check the account's Stripe billing for churn signals and, only after the user confirms, update the opportunity's next step to record them.

**Step 1: Find the opportunity in Salesforce**

Call `salesforce-get-opportunity` with `name.contains` set to `{opportunity-name}` and `closed` set to false. If more than one matches, list them (name, account, amount, close-date) and stop, asking which one. If none matches, say so and stop.

**Step 2: Carry the account to Stripe**

Call `salesforce-get-contact` with `account-id` set to the opportunity's account-id and collect the emails. Call `stripe-get-customer` with `email` set to each. If none matches, report that the account is not billed in Stripe and stop without writing.

**Step 3: Read churn signals**

For each matched customer-id, call `stripe-get-subscription` (customer-id), `stripe-get-invoice` (customer-id, status open) and `stripe-get-dispute` (customer-id). Signals: subscription status past_due, unpaid or canceled; cancel-at-period-end true; delinquent true; open invoices past due-date; open disputes. If there are no signals, report the account as healthy and stop without writing.

**Step 4: Propose the update and wait**

Show the current next-step and the proposed one: "Stripe churn risk: <signals, under 200 characters>". Keep any existing next-step text after it. Ask the user to confirm. Do not write until they say yes.

**Step 5: Write once, then confirm**

After a yes, call `salesforce-update-opportunity` once with `id` set to the opportunity-id and `next-step` set to the agreed text. Change no other field. Then call `salesforce-get-opportunity` with `opportunity-id` and report the stored next-step.

**Rules & Guidelines:**

* `salesforce-get-opportunity`, `salesforce-get-contact` and `salesforce-update-opportunity` are on the salesforce server. `stripe-get-customer`, `stripe-get-subscription`, `stripe-get-invoice` and `stripe-get-dispute` are on the stripe server.
* `salesforce-update-opportunity` is the only tool that may write, once, after the user confirms, and only the next-step field. Do not change stage, amount, probability or close-date. Do not call `salesforce-add-task`, `salesforce-update-account`, `salesforce-add-case` or any other salesforce add or update tool.
* `{risk-note}` (optional) is extra text from the user to append to the next step; leave it out when empty.

**Validation:**

* If the update returns an error, report it verbatim and stop.
* The join is contact email against Stripe customer email, matched case-insensitively and trimmed.