GitHub Copilot CLI session appeared to continue consuming AI credits after all visible tasks were completed.

## Summary

GitHub Copilot CLI session appeared to continue consuming AI credits after all visible tasks were completed.

## Environment

- GitHub Copilot CLI version: 1.0.75
- Mode: Interactive CLI session
- Session limit enabled: No
- Observed behavior: Session showed approximately 97.8% AI credit usage after the visible tasks completed. No further user prompts or interactions were made. Later, the session reached 100%.

## Expected behavior

After all visible tasks are complete and no user interaction occurs, AI credit usage should either remain stable or the CLI should clearly indicate that background work is still running and consuming credits.

## Actual behavior

The session moved from approximately 97.8% to 100% without additional user interaction.

## Question

Is this expected due to final response accounting, subagent completion, or background compaction? If so, can the CLI expose clearer status so users can distinguish between:
1. truly idle waiting-for-input state, and
2. background/session-finalization work that may still consume AI credits?

## Supporting context

GitHub documentation says session limits include model calls, subagents, and background work like compaction, and that session limits are soft caps because usage is only known after a response returns.

Start by reproducing the behavior in GitHub Copilot CLI 1.0.75 using an interactive session, then monitor credit usage after the visible task completes without further prompts. Compare the observed transition with the documented treatment of model calls, subagents, and background compaction; done means the post-task usage is explained and the idle or background state is clearly distinguishable.

Written by the indexing model from the issue text.