Implement thread message event listeners

Description:

Currently, there is a TODO in packages/api/src/EmbeddedChatApi.ts (line 239) that requires implementing logic to call thread message event listeners

Steps to reproduce:

1. Open a thread in a Rocket.Chat room
2. Send a message in the thread
3. Observe that thread message event listeners are not being called

Expected behavior:

• Thread messages should trigger event listeners
• Components listening to thread messages should receive updates in real-time
• Thread message events should be handled similarly to regular message events

Actual behavior:

• Thread message event listeners are not being invoked
• Components do not receive thread message updates
• The TODO comment indicates this functionality is not yet implemented

Implementation Notes:

• This should be implemented in the _doConnect() method (like other subscriptions)
• Should follow the existing pattern for message and notification subscriptions
• Needs to integrate with the callback system already in place

Start in packages/api/src/EmbeddedChatApi.ts at the TODO on line 239 and inspect _doConnect(). Compare the existing message and notification subscriptions and trace the callback system. Done means thread messages invoke the registered listeners and deliver real-time updates consistently with regular message events.