[FEATURE]:Show progress bar for Subagent #22153

Feature hasn't been suggested before.

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Describe the enhancement you want to request

When a foreground agent completes its task and waits for a sub-agent to execute its task, the TUI interface does not display any dynamic prompts indicating that the task is in progress. Although the user is prompted to "Ctrl+X down view subagents" this is not easily noticed and may mislead the user into believing that the current task has already finished.

Perhaps the foreground task's dynamic effects should be maintained while the background task is still running, allowing the user to intuitively perceive that the current task is still in progress.