A tag with a region (en-US, es-419) matches only that variant and reports a miss instead of taking another region. A bare tag takes the variant it means (pt -> pt-BR, es -> es-ES) and falls back to any variant only when that one is missing. `orig` prefers the title's own tag, `-sl orig` resolves, forced and SDH subtitles are picked from their own pools, and the track name no longer strips the region from the cached language.
BREAKING CHANGE: -l es-419 no longer selects es-ES, and language_priority, language_tags and muxing.default_language treat a regional tag as exact.
Error messages named the resolved language for a user who only ever defaulted to orig. Audio tracks now carry is_original, resolved through Tracks.by_language so it agrees with the downloader.
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