fix: typing indicator now shows on every message, not just the first

Two issues fixed:
- Use 'paused' instead of 'available' to stop typing. Baileys'
  sendPresenceUpdate('available') sends a global <presence> stanza and
  ignores the JID, so chatstate never left 'composing' and WhatsApp
  suppressed duplicate composing notifications per XEP-0085.
- Add setTyping call when piping messages to an already-running
  container. Previously only the first message (which spawns a new
  container) triggered the typing indicator.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/channels/whatsapp.test.ts

@@ -823,14 +823,14 @@ describe('WhatsAppChannel', () => {
       expect(fakeSocket.sendPresenceUpdate).toHaveBeenCalledWith('composing', 'test@g.us');
     });
 
-    it('sends available presence when stopping', async () => {
+    it('sends paused presence when stopping', async () => {
       const opts = createTestOpts();
       const channel = new WhatsAppChannel(opts);
 
       await connectChannel(channel);
 
       await channel.setTyping('test@g.us', false);
-      expect(fakeSocket.sendPresenceUpdate).toHaveBeenCalledWith('available', 'test@g.us');
+      expect(fakeSocket.sendPresenceUpdate).toHaveBeenCalledWith('paused', 'test@g.us');
     });
 
     it('handles typing indicator failure gracefully', async () => {