* fix(portals): treat an undetermined audio language as unknown
ICU 78, which Electron 43 and Node 26 ship, canonicalizes the ffprobe
marker `und` to the subtag `und` instead of an empty one. The source
metadata then recorded it as a stated language, so a switch between a
copy tagged `und` and one tagged English raised the "dub may differ"
warning. CI's older ICU hid this: the existing spec only fails on the
newer runtime.
Decline `und` explicitly, and cover `und-US` plus the dub comparison.
* test(portals): cover undetermined language across runtimes
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Co-authored-by: 4gray <serega05@gmail.com>
