upsertArtistSimilar keeps the existing matched path (top-K rows into
artist_similarity) and adds a parallel unmatched-persist loop with the
same top-K cap. Empty-name rows are skipped — we can't render a
suggestion card without a name. Logs unmatched-side errors at WARN
without aborting the tick (mirrors the matched-path policy).
bvandeusen
5e73f590a9