Remove vestigial surrogate/account-switcher scaffolding: activeSurrogateId cookie was scaffolded but NEVER set in git history (dead switcher UI); getSession still carries realUserId/isSurrogate/surrogates/canSwitchAccounts + SURROGATE_COOKIE-delete leftovers. NOTE users.surrogateOfUserId is a LIVE column (~19 files + surrogate emails) — that DATA model is real and must stay; only the dead cookie/switcher-UI scaffolding is removable. Split out of MARS-352 view-as (which uses a new viewAsUserId cookie, never touches surrogate rows). Low priority cleanup, reversible.