The museum server's EmailAuthorizationResponse declares
passkeySessionID, accountsUrl, twoFactorSessionID, and
twoFactorSessionIDV2 without `omitempty`, so Go always sends them,
as "" when unset. The previous mock omitted the unset fields
entirely, which let the ?? -based dispatch pass in tests while the
real server's "" defeated it and dual-2FA logins fell through to
the unsupported passkey branch.
sneak
2c51074294