Sub-agent thread opened using `/agent` should show the initial prompt too

What variant of Codex are you using?

Codex CLI

What feature would you like to see?

Currently, when you switch to a sub-agent thread, you can view the thread and follow it. However, you cannot see the initial prompt passed by the parent thread. This makes it hard to know what the parent thread assigned to this sub-agent thread.

One workaround that I've found is to ask the parent thread directly (often in a /side conversation) what prompt it wrote for the sub-agent. It will happily return the whole prompt verbatim.

Codex CLI should show the user sub-agent prompt in the sub-agent thread because it makes the thread more readable, helps user debug sub-agent execution when needed and just creates a more uniform, no-surprises experience for the Codex CLI user when they switch between the threads.

Additional information

_No response_