fix: export matrix account helpers in runtime api

extensions/matrix/runtime-api.ts

@@ -2,6 +2,10 @@
 // helpers without traversing the full plugin-sdk/runtime graph or bootstrapping
 // matrix-js-sdk during plain runtime-api import.
 export * from "./src/auth-precedence.js";
+export {
+  requiresExplicitMatrixDefaultAccount,
+  resolveMatrixDefaultOrOnlyAccountId,
+} from "./src/account-selection.js";
 export * from "./helper-api.js";
 export {
   assertHttpUrlTargetsPrivateNetwork,