custom agent show no invoke progress in batch mode by copilot -p

### Describe the feature or problem you'd like to solve

When copilot -p used and custom agent invoked there is no progress or status report

### Proposed solution

When copilot -p used and custom agent invoked there is no progress or status report. The timeline showing well when in interactive mode, but the timeline is missing in copilot -p mode, it makes user feel the copilot is hang there with no response until some file edits happened silently at background.

It will be useful to have below:
- show custom agent invoked with brief status like what the task dispatched to custom agent
- optionally the task progress status report from custom agent

### Example prompts or workflows

_No response_

### Additional context

_No response_