Support handoffs in Agent mode

[doggy8088]

Describe the feature or problem you'd like to solve

Copilot CLI doesn't support "handoffs" feature right now

Proposed solution

For Copilot CLI, when an Agent is executing a specified task, if that Agent has defined handoffs, it would be great if an option could be provided at the end to manage those handoffs

Example prompts or workflows

1. Use /agent switch to a plan agent.

2. Choose plan agent I assume.

3. Enter Plan a Sudoku game

4. Copilot CLI switch to implement agent automatically and put prompt in the input box.

   if multiple prompt available, show selection.

Additional context

No response

[EvanBoyle]

One feature we're working on here is allowing agents to call other agents cc @ellismg

[saw235]

Is it not enough to just expose a common tool such as call_agent()? That way any agent would have access to calling other agent