fix(auth): close diagnostic filesystem races

backend/test/auth-dynamic-registry.test.ts

@@ -6,6 +6,7 @@ import { stringify } from "yaml";
 import { buildApp, type AppWithAuthSessionStore } from "../src/app.js";
 import { loadAuthenticationConfig } from "../src/auth/config.js";
 import { loadConfig } from "../src/config.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";
@@ -47,9 +48,11 @@ test("each login and session resolve uses the current config snapshot users file
   chmodSync(authFile, 0o600);
   chmodSync(usersAFile, 0o600);
   chmodSync(usersBFile, 0o600);
+  const authStateRoot = join(directory, "auth-state");
+  prepareAuthStateRoot(authStateRoot);
   const app = buildApp(loadConfig({
     THT_AUTH_CONFIG_FILE: authFile,
-    THT_AUTH_STATE_ROOT: join(directory, "auth-state"),
+    THT_AUTH_STATE_ROOT: authStateRoot,
     THT_HARNESS_DIR: "/tmp/h",
   }));
   cleanups.push(async () => {