cross-sport/era-adjusted-board.ts (S245/S246)
The second BROWSABLE cross-sport leaderboard. Each sport now ships an era-TRANSLATED single-season board built by the shared era-adjusted-core (robust-z within each (season, position-group) peer bucket, re-projected onto the group's most-recent rated season). Raw translated VAL is NOT comparable across sports — a translated 35.8 for a running back is not a translated 20.2 for a forward. But the underlying robust z-score IS: it is unit-free, meaning "how many robust standard deviations above your own era's positional peers," the same thing in every sport. So the cross-sport hub ranks the single greatest era-translated seasons by z — the honest cross-sport axis, exactly parallel to how the prominence board (S242) ranks careers by within-sport percentile.
NFL rides its z-native board at data/nfl/era-translated-seasons.json (its legacy per-game era-adjusted board is a different engine and stays at era-adjusted-seasons.json); NBA/NHL/MLB ride data/{sport}/era-adjusted-seasons.json.
The pure transforms (merge/filter/decade/position/twins) live in the client-safe core (era-adjusted-board-core.ts, no node:fs) and are re-exported here so existing server importers and tests are unchanged; only this file touches the filesystem.