Invite Salesforce campaign contacts to Mailchimp with double opt-in

**Objective:** Add the people in the Salesforce campaign named `{salesforce-campaign}` to the Mailchimp audience named `{audience-name}`, as pending members who receive a double opt-in confirmation email.

**Step 1: Find the audience**

Call `mailchimp-get-list` with `name` set to `{audience-name}`. If nothing matches exactly, call it again with `name.contains` and list the matches, then stop so the user can choose. Keep the list-id.

**Step 2: Collect the Salesforce members**

Call `salesforce-get-campaign` with `name` set to `{salesforce-campaign}`; if more than one matches, list them and stop. Call `salesforce-get-campaign-member` with that `campaign-id`. Keep email and name for each member, and drop members with no email. Split name into a first name and a last name at the last space.

**Step 3: Remove anyone already handled**

For each email, call `mailchimp-get-list-member` with `email` set to that address and `list-name` set to `{audience-name}`. Drop anyone already in the audience, whatever their status. Never re-add someone whose status is unsubscribed or cleaned.

**Step 4: Confirm**

Show the people to be added: email, first name, last name. Say that each will get a Mailchimp confirmation email and will only join once they confirm. Ask the user to confirm. Do not continue without an explicit yes.

**Step 5: Add**

For each confirmed person, call `mailchimp-add-list-member` once with `list-id`, `email-address`, `first-name`, `last-name` and `status` set to pending.

**Step 6: Report**

The people added, then those skipped and why (no email, already in the audience, unsubscribed or cleaned), and any failures.

**Rules & Guidelines:**

* `mailchimp-get-list`, `mailchimp-get-list-member` and `mailchimp-add-list-member` are on the mailchimp server. `salesforce-get-campaign` and `salesforce-get-campaign-member` are on the salesforce server.
* The only write this prompt may make is `mailchimp-add-list-member`, with `status` set to pending, after the user confirms. Never set status to subscribed: Salesforce campaign membership is not email consent. Do not call `mailchimp-update-list-member`, `mailchimp-add-segment-member` or any salesforce add or update tool.

**Validation:**

* Compare email addresses case-insensitively.
* If nobody is left after Step 3, say so and stop without asking for confirmation.
* If an add fails, report the error and continue with the rest without retrying.