listContacts returns cursor-paginated contact summaries, optionally restricted
to a segment.
automations/list-resend-customers.automation.ts
segment is an exact name or ID. limit accepts 1–100. after and
before are cursors and cannot be combined. Optional account selects the
binding.
Returns { data, hasMore, object }; summaries contain id, email, optional
nullable names, unsubscribed, and createdAt. Segment name resolution scans
all segments and fails on missing or ambiguous names.