Turn a DonorPerfect flag into a Mailchimp segment, opt-outs left out

**Objective:** Add every DonorPerfect donor carrying the flag `{flag}` to the Mailchimp static segment or tag `{segment-name}`, so the group can be targeted in Mailchimp.

**Step 1: Find the segment**

Call `mailchimp-get-segment` with `name` set to `{segment-name}`. If there is not exactly one match, list the candidates (name, type, audience list id) and stop. If its type is not static (a saved segment built from conditions), say members cannot be added to it directly and stop. Note `segment-id` and `list-id`.

**Step 2: Read the flagged donors**

Call `donorperfect-get-flag` with `flag` set to `{flag}`. For each `donor-id`, call `donorperfect-get-donor` with `donor-id` and keep donors with a non-empty `email`.

**Step 3: Check Mailchimp for each donor**

For each donor email, call `mailchimp-get-segment-member` with `segment-id` and `email`; skip donors already in the segment. For the rest, call `mailchimp-get-list-member` with `email` and keep only those who are members of the segment's audience (matching `list-id`) with status `subscribed` or `pending`. A segment can only hold existing audience members, so list the others as not in the audience.

**Step 4: Confirm before writing**

Show the donors to add (donor id, name, email), plus the counts already in the segment, not in the audience, and without an email. Ask the user to confirm. Do not write until they do.

**Step 5: Add to the segment**

For each confirmed donor, call `mailchimp-add-segment-member` with `segment-id`, `list-id` and `email-address`. Record any failure and continue.

**Step 6: Report**

Added, already present, not in audience, no email and failed counts, with the added rows. Suggest the add-donors-to-audience prompt for the donors not in the audience.

**Rules & Guidelines:**

* `donorperfect-get-flag` and `donorperfect-get-donor` are on the donorperfect server. `mailchimp-get-segment`, `mailchimp-get-segment-member`, `mailchimp-get-list-member` and `mailchimp-add-segment-member` are on the mailchimp server.
* `mailchimp-add-segment-member` is the only write, only after Step 4 confirmation. Do NOT call `mailchimp-add-list-member` or `mailchimp-update-list-member` here, and do not change anything in DonorPerfect.

**Validation:**

* If no donor carries the flag, say so and stop.
* Never add an unsubscribed or cleaned member to the segment.