feat: compose executable frontend runtime

tests/unit/auth-session-adapter.test.js

@@ -2,6 +2,7 @@ import { describe, expect, it, vi } from "vitest";
 
 import {
   createAnonymousSessionAdapter,
+  createDemoSessionAdapter,
   createExternalAuthSessionAdapter,
 } from "../../src/adapters/auth/external-session-adapter.js";
 
@@ -9,6 +10,9 @@ describe("external AuthSessionPort adapter", () => {
   it("attaches opaque credentials without exposing a token-shaped session", async () => {
     const adapter = createExternalAuthSessionAdapter({
       readState: () => "authenticated",
+      subscribe: () => () => {},
+      beginSignIn: async () => {},
+      signOut: async () => {},
       attachCredential: async (request) => {
         const headers = new Headers(request.headers);
         headers.set("X-Session-Attached", "true");
@@ -28,6 +32,9 @@ describe("external AuthSessionPort adapter", () => {
   it("fails invalid recovery states closed", async () => {
     const adapter = createExternalAuthSessionAdapter({
       readState: () => "authenticated",
+      subscribe: () => () => {},
+      beginSignIn: async () => {},
+      signOut: async () => {},
       attachCredential: async (request) => request,
       recoverSession: async () => "unexpected",
       notifyUnauthenticated: vi.fn(),
@@ -41,4 +48,20 @@ describe("external AuthSessionPort adapter", () => {
     expect(adapter.getState()).toBe("unauthenticated");
     await expect(adapter.recover()).resolves.toBe("no-session");
   });
+
+  it("provides a reactive credential-free demo seam", async () => {
+    const adapter = createDemoSessionAdapter();
+    let notifications = 0;
+    const unsubscribe = adapter.subscribe(() => {
+      notifications += 1;
+    });
+
+    expect(adapter.getState()).toBe("unauthenticated");
+    await adapter.beginSignIn("/");
+    expect(adapter.getState()).toBe("authenticated");
+    await adapter.signOut();
+    expect(adapter.getState()).toBe("unauthenticated");
+    expect(notifications).toBe(2);
+    unsubscribe();
+  });
 });