Integrate asynchronous questions into the TUI

[copyberry]

Integrate asynchronous questions into the TUI

What changed

• Display questions from live agent messages with a collapsed question count and an expandable answer editor.
• Support navigating, answering, queueing, and skipping questions while preserving the main composer draft. Expose question navigation and skip actions in the keymap picker.
• Route answers through existing input delivery and consume them only after an accepted send or queue operation. Keep questions editable while disconnected, with delivery and skipping disabled.

Testing

Add tests for answer delivery, queued answers, retained drafts, disconnected editing, Vim undo, buffered input, constrained layouts, and question shortcut descriptions.

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