jellyfinFieldMapping.ts (SORT_FIELD_MAP friendly->Jellyfin sort names) had
zero consumers — sort code passes raw Jellyfin field names directly — so it
and its test are deleted.
playbackUnits.ts can't be removed: its tick<->seconds helpers are still the
correct converters for the remote Jellyfin *session* boundary
(SessionInfo.playState.positionTicks, NowPlayingItem.runTimeTicks), which
legitimately arrives in ticks. Documented that narrowed role; formatTime/
calculateProgress remain neutral seconds-based presentation helpers.
Note (out of scope): sortBy still passes raw Jellyfin field names
("SortName", "CommunityRating") — a separate sort-taxonomy leak that would
need its own Rust SortKey, like the search-scope work.
Frontend 626 tests (jellyfinFieldMapping's 18 removed with it), check clean.