feat(gateway): add sender presence tracking

src/channels/registry.test.ts

@@ -132,6 +132,71 @@ describe('ChannelRegistry', () => {
     expect(adapter.sendFn).toHaveBeenCalledWith('user-42', { text: 'pong' });
   });
 
+  it('tracks presence from inbound messages', async () => {
+    const adapter = createMockAdapter('test-channel');
+    registry.register(adapter);
+    registry.setMessageHandler(async () => {});
+
+    adapter.triggerMessage(makeMessage('test-channel'));
+
+    await vi.waitFor(() => {
+      expect(registry.getPresence()).toHaveLength(1);
+    });
+
+    const [presence] = registry.getPresence();
+    expect(presence.channel).toBe('test-channel');
+    expect(presence.senderId).toBe('user-42');
+    expect(presence.messageCount).toBe(1);
+    expect(presence.status).toBe('online');
+  });
+
+  it('marks presence offline after inactivity window', async () => {
+    vi.useFakeTimers();
+    try {
+      registry = new ChannelRegistry({ offlineAfterMs: 1000 });
+      const adapter = createMockAdapter('test-channel');
+      registry.register(adapter);
+      registry.setMessageHandler(async () => {});
+
+      adapter.triggerMessage(makeMessage('test-channel'));
+      await vi.runAllTimersAsync();
+
+      vi.advanceTimersByTime(1500);
+      const [presence] = registry.getPresence();
+      expect(presence.status).toBe('offline');
+    } finally {
+      vi.useRealTimers();
+    }
+  });
+
+  it('filters presence by channel and status', async () => {
+    vi.useFakeTimers();
+    try {
+      registry = new ChannelRegistry({ offlineAfterMs: 1000 });
+      const a1 = createMockAdapter('telegram');
+      const a2 = createMockAdapter('discord');
+      registry.register(a1);
+      registry.register(a2);
+      registry.setMessageHandler(async () => {});
+
+      a1.triggerMessage(makeMessage('telegram'));
+      a2.triggerMessage({ ...makeMessage('discord'), senderId: 'user-99' });
+      await vi.runAllTimersAsync();
+      vi.advanceTimersByTime(1500);
+      a2.triggerMessage({ ...makeMessage('discord'), senderId: 'user-99' });
+
+      const telegramOnly = registry.getPresence({ channel: 'telegram' });
+      expect(telegramOnly).toHaveLength(1);
+      expect(telegramOnly[0].channel).toBe('telegram');
+
+      const onlineOnly = registry.getPresence({ status: 'online' });
+      expect(onlineOnly).toHaveLength(1);
+      expect(onlineOnly[0].channel).toBe('discord');
+    } finally {
+      vi.useRealTimers();
+    }
+  });
+
   it('routes reply using metadata.replyPeerId when provided', async () => {
     const adapter = createMockAdapter('test-channel');
     registry.register(adapter);