Copilot CLI gets stuck showing 'updating plan' after completion

[lpolish]

Bug
The terminal UI can remain on "updating plan" even after the work is complete and the response has finished.

Expected
The status should switch to completed or stop indicating an active task once the step is done.

Actual
The terminal still appears to be working, which makes a finished task look unfinished.

Impact
Confusing UX; it caused me to think the agent was still running after it had already finished.

Repro

1. Start a task that updates the plan.
2. Wait for the work to finish.
3. The terminal can still show "updating plan" instead of a finished state.

[lpolish]

Additional device info:

• OS: Ubuntu 24.04.4 LTS
• Kernel: Linux 6.8.0-101-generic (x86_64)

This was observed in a terminal session on this Linux machine.