Free, capped preview of the person-grain topic direction: given a
topic_id, return a small sample (up to 25) of the top people (as HEMs),
ranked by perc_score, plus the topic's total count. Use it to show a
teaser while configuring a source, then call the paid /api/v1/intent/people
to pull and pay for the full list.

Nothing is billed. Distinct from dry_run (which returns a cost count and no
records): this returns actual sample records. It does not paginate (no
cursor, no next_cursor) and never returns seen_email; you always get the
strongest-intent top of the list. count is the topic's full people total,
so the sample is only a window onto it.