Routing, parameters, and loading

Routes are immutable and belong to one ERSC identity.
page(path, page) attaches a Page; mount(prefix, routes) nests a route scope.
Mounted scopes retain their Layout and Loading ancestry.
On GET/HEAD, the request handler decodes Page parameters once before rendering, with services from existing route middleware available. Rejected parameters return an empty 404, including navigation Flight.
Server Function POST refreshes keep parameter rejection in React's render-error path, preserving the completed action result.
Effect HTTP owns route matching; ERSC rejects duplicate shapes and invalid composition while building the graph.