Rails matching req, filtered by disabled/available(), ranked by
priority (unlisted rails keep insertion order, after listed ones).
Optionalprefs: RouterPreferencesRemove a rail by id.
Top-ranked option's quote. Throws when nothing routes, or
AmbiguousRouteError when tieBreak is "require-choice" and
more than one option survives.
Optionalprefs: RouterPreferences
Registry-based payment router. Holds id-keyed PaymentRail entries (mirroring
ActivityRegistry):use()overwrites by id,remove()deletes. It operates on a PaymentRequest (raw target + optional amount) — rails self-extract their target via the shared helpers, andavailable()gates on the amount.options()returns every matching+available rail ranked by preferences;route()is the "take the top" convenience.