Refactor API and enhance Angular integration

- Removed `ciTargetName` from `nx.json`.
- Updated `package.json` to include new dependencies: `@types/seedrandom`, `fast-check`, `happy-dom`, and `@nestjs/schedule`.
- Modified `pnpm-lock.yaml` to reflect the addition of new packages and their versions.
- Improved project documentation in `PROJECT_CONTEXT.md` to clarify the use of Zod schemas and Angular framework decisions.
- Introduced new Angular components and patterns in the `.agents/skills/frontend-angular` directory, including examples and reference materials for Angular 21+ features.

apps/overlay/src/app/twitch/twitch-auth.service.spec.ts

@@ -0,0 +1,107 @@
+import { TwitchAuthService, TwitchJwtPayload } from './twitch-auth.service';
+
+function makeJwt(payload: Partial<TwitchJwtPayload> = {}): string {
+  const full: TwitchJwtPayload = {
+    exp: Math.floor(Date.now() / 1000) + 3600,
+    opaque_user_id: 'U12345678',
+    user_id: '12345678',
+    channel_id: '987654321',
+    role: 'viewer',
+    ...payload,
+  };
+  const encoded = btoa(JSON.stringify(full))
+    .replace(/\+/g, '-')
+    .replace(/\//g, '_')
+    .replace(/=/g, '');
+  return `eyJhbGciOiJIUzI1NiJ9.${encoded}.sig`;
+}
+
+function makeTwitchAuth(payload: Partial<TwitchJwtPayload> = {}): TwitchAuth {
+  return {
+    channelId: payload.channel_id ?? '987654321',
+    clientId: 'test_client',
+    token: makeJwt(payload),
+    userId: payload.opaque_user_id ?? 'U12345678',
+  };
+}
+
+describe('TwitchAuthService', () => {
+  let service: TwitchAuthService;
+  let extCallbacks: {
+    onAuthorized?: (auth: TwitchAuth) => void;
+    onContext?: (ctx: TwitchContext, changed: (keyof TwitchContext)[]) => void;
+    onVisibilityChanged?: (visible: boolean, ctx: TwitchContext) => void;
+  };
+
+  beforeEach(() => {
+    extCallbacks = {};
+    (window as Window & { Twitch?: unknown }).Twitch = {
+      ext: {
+        onAuthorized: (cb: (auth: TwitchAuth) => void) => { extCallbacks.onAuthorized = cb; },
+        onContext: (cb: (ctx: TwitchContext, changed: (keyof TwitchContext)[]) => void) => { extCallbacks.onContext = cb; },
+        onVisibilityChanged: (cb: (visible: boolean, ctx: TwitchContext) => void) => { extCallbacks.onVisibilityChanged = cb; },
+        listen: () => undefined,
+        unlisten: () => undefined,
+        send: () => undefined,
+      },
+    };
+
+    service = new TwitchAuthService();
+    service.init();
+  });
+
+  afterEach(() => {
+    delete (window as Window & { Twitch?: unknown }).Twitch;
+  });
+
+  it('exposes null auth before onAuthorized fires', () => {
+    expect(service.auth()).toBeNull();
+    expect(service.jwtPayload()).toBeNull();
+    expect(service.isLoggedIn()).toBe(false);
+    expect(service.channelId()).toBeNull();
+  });
+
+  it('sets auth and decoded payload when onAuthorized fires', () => {
+    extCallbacks.onAuthorized!(makeTwitchAuth());
+
+    expect(service.auth()).not.toBeNull();
+    expect(service.jwtPayload()?.opaque_user_id).toBe('U12345678');
+    expect(service.jwtPayload()?.channel_id).toBe('987654321');
+    expect(service.channelId()).toBe('987654321');
+  });
+
+  it('reports isLoggedIn true for U-prefixed opaque_user_id', () => {
+    extCallbacks.onAuthorized!(makeTwitchAuth({ opaque_user_id: 'U99999999' }));
+    expect(service.isLoggedIn()).toBe(true);
+  });
+
+  it('reports isLoggedIn false for A-prefixed opaque_user_id', () => {
+    extCallbacks.onAuthorized!(makeTwitchAuth({ opaque_user_id: 'Aanonymous' }));
+    expect(service.isLoggedIn()).toBe(false);
+  });
+
+  it('defaults isVisible to true', () => {
+    expect(service.isVisible()).toBe(true);
+  });
+
+  it('updates isVisible when onVisibilityChanged fires', () => {
+    const ctx = {} as TwitchContext;
+    extCallbacks.onVisibilityChanged!(false, ctx);
+    expect(service.isVisible()).toBe(false);
+
+    extCallbacks.onVisibilityChanged!(true, ctx);
+    expect(service.isVisible()).toBe(true);
+  });
+
+  it('updates context when onContext fires', () => {
+    const ctx = { game: 'test-game' } as TwitchContext;
+    extCallbacks.onContext!(ctx, ['game']);
+    expect(service.context()?.game).toBe('test-game');
+  });
+
+  it('updates context from onVisibilityChanged', () => {
+    const ctx = { isFullScreen: true } as TwitchContext;
+    extCallbacks.onVisibilityChanged!(false, ctx);
+    expect(service.context()?.isFullScreen).toBe(true);
+  });
+});