IGPAPI
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    Type Alias MediaInfoSourceResult

    MediaInfoSourceResult:
        | { ok: true; source: MediaInfoSource }
        | { ok: false; reason: "no-media" | "carousel-index" }

    The reader's answer: the source, or why the answer cannot be acted on — no media at all, or a carouselIndex the media does not hold (a non-zero index on a single media included). Each caller turns the reason into its own typed error before any like or note goes out.