Background tasks talk to you through the chat

When the agent hands work to a background task, you now follow it and answer it in the chat:

• The task's card stays in sight in the chat while the task works or waits, instead of folding into the agent's steps.
• When a task pauses at its credit budget, the chat shows a pause card: what the task finished, what is left, and one Continue button. Before, you had to open the task and find the button inside it.
• A task's own view is now read-only, with a Back to chat button. To change a task, write to the agent in the chat. Before, words typed inside a task never reached the agent, and it could undo what you asked for.