feat(auth): re-export authManifest + AuthManifest from package root

packages/auth/src/index.ts

@@ -43,3 +43,8 @@ export {
   type UserSignedUpEvent,
 } from "./events/user-signed-up.event";
 // <gen:realtime-channels>
+
+// Feature conformance manifest (added in conformance milestone i, exposed
+// here in milestone ii so the boot-time assertion and future tooling can
+// read the contract from the package boundary).
+export { authManifest, type AuthManifest } from "./feature.manifest";