[Agent Builder] Show HITL questions and approval requests from events

Render clarifying questions and tool approval requests from both live execution state and saved conversation events.

- Show outstanding questions and approvals while awaiting a human response.
- Preserve the existing conversation-input restrictions.
- Submit the human response and continue execution.
- Display submitted answers with the correct question or approval context.
- Ensure refreshing or reopening the conversation restores the same outstanding prompt.
- Verify that the continued execution and its saved events remain associated with the correct human response.