fix(auth): close diagnostic filesystem races

backend/test/auth-routes-local.test.ts

@@ -6,6 +6,7 @@ import { stringify } from "yaml";
 import { buildApp } from "../src/app.js";
 import { loadConfig } from "../src/config.js";
 import { LoginFailureLimiter } from "../src/auth/routes.js";
+import { prepareAuthStateRoot } from "./auth-test-fixtures.js";
 
 const password = "correct horse battery staple";
 const passwordHash = "$argon2id$v=19$m=65536,t=3,p=1$AAECAwQFBgcICQoLDA0ODw$DRo8ZSPI8G5OCvnFFapbVEjP69aDjy1Sw9i2743cPC4";
@@ -82,6 +83,7 @@ async function createLocalApp(options: {
   writeFileSync(usersFile, usersYaml({ enabled: options.enabled }), { encoding: "utf8", mode: 0o600 });
   chmodSync(authConfigFile, 0o600);
   chmodSync(usersFile, 0o600);
+  prepareAuthStateRoot(authStateRoot);
   const app = buildApp(loadConfig({
     THT_AUTH_CONFIG_FILE: authConfigFile,
     THT_AUTH_STATE_ROOT: authStateRoot,
@@ -151,6 +153,7 @@ test("remembered login uses a persistent secure cookie under an HTTPS public URL
   writeFileSync(usersFile, usersYaml(), { encoding: "utf8", mode: 0o600 });
   chmodSync(authConfigFile, 0o600);
   chmodSync(usersFile, 0o600);
+  prepareAuthStateRoot(authStateRoot);
   const config = () => loadConfig({ THT_AUTH_CONFIG_FILE: authConfigFile, THT_AUTH_STATE_ROOT: authStateRoot, THT_HARNESS_DIR: "/tmp/h" });
   const first = buildApp(config());
   try {