Warn account owners when a Stripe payment fails mid-deal

**Objective:** List the Stripe customers with failed payments in the last `{lookback-days}` days (default 30) whose Salesforce account still has open opportunities, so the account owner can act before the deal moves. Only include opportunities of at least `{min-opportunity-amount}` (default: any amount).

**Step 1: Collect failed payments in Stripe**

Call `stripe-get-charge` with `status` set to failed and `created.from` set to today minus the lookback. Then call `stripe-get-invoice` with `status` set to open and `due-date.to` set to today to catch invoices already past due. Group the results by customer email, keeping customer-id, the failed amounts, the latest failure-message and the open amount-remaining.

**Step 2: Carry each email to Salesforce**

For each customer email, call `salesforce-get-contact` with `email` set to it. If nothing comes back, keep the customer in a separate list headed "In Stripe, not in Salesforce" and continue.

**Step 3: Find open opportunities on the account**

For each matched contact with an account-id, call `salesforce-get-opportunity` with `account-id` set to it and `closed` set to false (add `amount.min` set to `{min-opportunity-amount}` when given). Drop accounts with no open opportunity.

**Step 4: Report**

A table sorted by open opportunity amount, largest first: account name, account owner, contact email, Stripe customer-id, failed charge count and total, latest failure-message, open invoice amount-remaining, open opportunity names with stage, amount and close-date. Then the "In Stripe, not in Salesforce" list.

**Rules & Guidelines:**

* `stripe-get-charge` and `stripe-get-invoice` are on the stripe server. `salesforce-get-contact` and `salesforce-get-opportunity` are on the salesforce server.
* The join is the Stripe customer email against the Salesforce contact email, matched case-insensitively and trimmed.
* This is read-only. Do not call `salesforce-add-task`, `salesforce-add-case`, `salesforce-update-opportunity`, `salesforce-update-account`, `salesforce-update-contact` or any other salesforce add or update tool. Use the log-payment-follow-up prompt to record a follow-up.

**Validation:**

* If Stripe returns no failed charges and no past-due invoices, say so and stop.
* A charge with no customer email cannot be joined; list it by charge-id under "Unmatched".
* Never add amounts in different currencies together.