Judge a candidate feed for a product BEFORE adding it as a station. Writes nothing.

Body: {"product_id", "rss_url"} to have the brain fetch the feed, or {"product_id", "entries": [...]} with up to 50 entries your own client read (same shape as /scout/ingest; required for feeds marked read_by: client). Optional "sample": how many best-matching posts the panel judges (1-12, default 8; one judgement each).