Pure query functions over AppSurface data.
Usable in tests, the adversarial auth runner, and future surface explorer UI.
Replaces duplicated inline .filter() patterns.
TODO @surface-explorer Used by test utilities (test_auth_surface, adversarial_input,
surface_invariants) and SurfaceExplorer.svelte (surface_auth_summary, format_route_key).
Several query functions (filter_authenticated_routes, filter_keeper_routes,
routes_by_auth_type, filter_routes_by_prefix) are pre-built for richer surface
explorer features and consumer test suites — leverage more as the surface UI matures.