feat(push): plumb hostname-aware prefix into Web Push notifications

Closes the Web Push gap left by #82: in-page Notification API and tab
title flash both showed `codeman:<host>` after that PR, but OS-level
notifications dispatched via the service worker — the surface that
matters most when the tab is closed and the user is reading their
system notification center across multiple Codeman instances —
still hardcoded the literal "Codeman" prefix.

Service workers run in an isolated context with no access to
document.title or any in-page state, so the hostname has to ride
along in the push payload itself.

Server (server.ts:sendPushNotifications): emit `hostTitle: this.windowTitle`
in the JSON payload alongside the existing `title` (event-specific text
like "Permission Required"). The two stay separate so the SW can compose
them — the server knows the host, the SW knows the OS context.

Service worker (sw.js): compose `${hostTitle}: ${title}` when both
present, mirroring the in-page Notification format from
notification-manager.js. Fall back to `title || hostTitle || 'Codeman'`
so older servers (which omit hostTitle) keep working — the field is
purely additive on the wire.

Tests (test/push-payload-host-title.test.ts): mock the `web-push` module
via vi.hoisted(), instantiate WebServer without binding a port, stub
the push store with one fake subscription, and verify the JSON payload
shipped to webpush.sendNotification carries the right hostTitle for
both --title-hostname overrides and the os.hostname() default. Also
mirrors the SW's title-composition logic in a small helper so any
future change to the format breaks the test instead of being caught
only by users running multiple Codeman instances.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

test/push-payload-host-title.test.ts

@@ -0,0 +1,165 @@
+/**
+ * Verifies that web-push payloads include the hostname-aware `hostTitle`
+ * field so service-worker OS notifications can disambiguate Codeman
+ * instances on multiple machines (laptop / dev box / NAS).
+ *
+ * The in-page Notification path (notification-manager.js) prefixes with
+ * `${originalTitle}: ${title}` reading from `document.title`. The service
+ * worker has no access to document.title, so the server must ship the
+ * prefix in the push payload itself.
+ *
+ * Strategy: mock the `web-push` module, instantiate WebServer (no port
+ * binding — start() is never called), stub the push store with one fake
+ * subscription, then call the private sendPushNotifications and inspect
+ * the JSON payload handed to webpush.sendNotification.
+ *
+ * Port: N/A (no server start)
+ */
+
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+
+// vi.mock is hoisted to the top of the file, so factory captures must use
+// vi.hoisted() to be initialized before the mocked import is evaluated.
+const { sendNotification, setVapidDetails, generateVAPIDKeys } = vi.hoisted(() => ({
+  sendNotification: vi.fn(async () => undefined),
+  setVapidDetails: vi.fn(),
+  generateVAPIDKeys: vi.fn(() => ({
+    publicKey: 'test-public-key',
+    privateKey: 'test-private-key',
+  })),
+}));
+
+vi.mock('web-push', () => ({
+  default: { sendNotification, setVapidDetails, generateVAPIDKeys },
+}));
+
+import { WebServer } from '../src/web/server.js';
+
+interface PushPayload {
+  title: string;
+  hostTitle?: string;
+  body: string;
+  tag: string;
+  sessionId: string;
+  urgency: string;
+  actions?: Array<{ action: string; title: string }>;
+}
+
+function makeServerWithHost(host: string): WebServer {
+  // Constructor only assigns fields — no network/disk activity until start().
+  const server = new WebServer(0, false, true, host);
+  // Stub push store: one subscription with all events enabled.
+  const fakeSub = {
+    endpoint: 'https://push.example.com/abc',
+    keys: { p256dh: 'k1', auth: 'k2' },
+    pushPreferences: {} as Record<string, boolean>,
+  };
+  const stubStore = {
+    getAll: () => [fakeSub],
+    getVapidKeys: () => ({ publicKey: 'pub', privateKey: 'priv', generatedAt: 0 }),
+    removeByEndpoint: vi.fn(),
+  };
+  (server as unknown as { pushStore: typeof stubStore }).pushStore = stubStore;
+  return server;
+}
+
+function lastPayload(): PushPayload {
+  expect(sendNotification).toHaveBeenCalled();
+  const call = sendNotification.mock.calls[sendNotification.mock.calls.length - 1];
+  return JSON.parse(call[1] as string) as PushPayload;
+}
+
+describe('push payload hostTitle (Web Push hostname plumbing)', () => {
+  beforeEach(() => {
+    sendNotification.mockClear();
+    setVapidDetails.mockClear();
+  });
+
+  it('includes hostTitle = codeman:<titleHostname> in the payload', () => {
+    const server = makeServerWithHost('laptop');
+    (
+      server as unknown as {
+        sendPushNotifications: (e: string, d: Record<string, unknown>) => void;
+      }
+    ).sendPushNotifications('hook:idle_prompt', {
+      sessionId: 's-1',
+      sessionName: 'mysession',
+    });
+
+    const payload = lastPayload();
+    expect(payload.hostTitle).toBe('codeman:laptop');
+    // The bare event title is preserved separately so the SW can compose them.
+    expect(payload.title).toBe('Waiting for Input');
+  });
+
+  it('falls back to os.hostname() when --title-hostname is not provided', () => {
+    const server = makeServerWithHost(''); // empty -> constructor uses getHostname()
+    (
+      server as unknown as {
+        sendPushNotifications: (e: string, d: Record<string, unknown>) => void;
+      }
+    ).sendPushNotifications('hook:permission_prompt', {
+      sessionId: 's-2',
+      sessionName: 'sess',
+      tool_name: 'Bash',
+    });
+
+    const payload = lastPayload();
+    expect(payload.hostTitle).toMatch(/^codeman:.+/);
+    expect(payload.hostTitle).not.toBe('codeman:');
+    expect(payload.title).toBe('Permission Required');
+  });
+
+  it('different WebServer instances ship distinct hostTitles', () => {
+    const a = makeServerWithHost('host-a');
+    const b = makeServerWithHost('host-b');
+
+    (
+      a as unknown as {
+        sendPushNotifications: (e: string, d: Record<string, unknown>) => void;
+      }
+    ).sendPushNotifications('hook:stop', { sessionId: 's-a', sessionName: 'A' });
+    (
+      b as unknown as {
+        sendPushNotifications: (e: string, d: Record<string, unknown>) => void;
+      }
+    ).sendPushNotifications('hook:stop', { sessionId: 's-b', sessionName: 'B' });
+
+    expect(sendNotification).toHaveBeenCalledTimes(2);
+    const first = JSON.parse(sendNotification.mock.calls[0][1] as string) as PushPayload;
+    const second = JSON.parse(sendNotification.mock.calls[1][1] as string) as PushPayload;
+    expect(first.hostTitle).toBe('codeman:host-a');
+    expect(second.hostTitle).toBe('codeman:host-b');
+  });
+});
+
+// ─── SW display-title formatting ─────────────────────────────────────────
+// The SW logic at sw.js:130 composes the OS notification title from the
+// payload. It's a 3-line conditional we mirror here so any future change
+// (e.g. swapping the separator) shows up in this test instead of being
+// caught only by users running multiple Codeman instances.
+
+function computeSwDisplayTitle(payload: { title?: string; hostTitle?: string }): string {
+  const { title, hostTitle } = payload;
+  return hostTitle && title ? `${hostTitle}: ${title}` : title || hostTitle || 'Codeman';
+}
+
+describe('service worker displayTitle composition (mirrors sw.js)', () => {
+  it('joins host and title with ": " when both present', () => {
+    expect(computeSwDisplayTitle({ hostTitle: 'codeman:laptop', title: 'Permission Required' })).toBe(
+      'codeman:laptop: Permission Required'
+    );
+  });
+
+  it('falls back to bare title when hostTitle is missing (older server)', () => {
+    expect(computeSwDisplayTitle({ title: 'Permission Required' })).toBe('Permission Required');
+  });
+
+  it('falls back to hostTitle alone when title is missing', () => {
+    expect(computeSwDisplayTitle({ hostTitle: 'codeman:laptop' })).toBe('codeman:laptop');
+  });
+
+  it('defaults to "Codeman" when both missing', () => {
+    expect(computeSwDisplayTitle({})).toBe('Codeman');
+  });
+});